"is there a rule of thumb?"
How high rise are your current bars? (And how wide are they)
What length and rise angle is your current stem?

Where do your bars sit (vertically) in relation to your saddle at full pedalling height? And where would they be ideally?

You could work out any change in position exactly (and add in horizontal position in relation to the saddle) in excel providing you know the head angle of the bike. A bit long winded but you could see all your bar/stem options next to one another and work out what would put your bars where
Not that I've done this before ..

"my am40s"
(partly) White (waffle sole) shoes? in the peak? In january?
They'll never be the same again ..

What drop in what 'quarry' that may or may not be cavedale (despite cavedale not being a quarry), so pindale? which drop?

"I'd be interested to see a 4×4 coping with the Kentmere side without a) a winch b) remodelling"
Having seen a stock Nissan Terrano make it up the bad side of (ie southwards) Roych Clough (Kinder Scout Loop, Peak District), I wouldn't be suprised if Garburn was doable unmodified, the really bad bit of walna scar, perhaps not

"Not really given how **** slowly they go down hills whenever I've seen them"
The 4x4s yes, the Motocrossers much less so. Same seems to go for the uphills. I'm not so keen on a MX bike at full throttle tearing past me on a rough narrow lane/track of a climb

"set the spanner so it and the crank form a 'V' shape and squeeze them together (Sometimes with one hand"
Yes, do this, though when its really stick I much prefer to stand on the allen key instead. Lean on the saddle to stop the rear wheel slipping and the resistance will come (presuming your 'set it up' right from the freewheel being 'locked' (not free) as it were

Better still use a peice of metal tube that will slide over the end of the proper spanner/allen key snugly, letting you undo it easily gently by and, or if you're willing to risk rounding the allen key head/spanner flat edges, standing on it ..

Right is right, Left is wrong (ie reverse thread). Thats how I remember

" you put anything else in the bike bag/box they could [& have] charged excess fees"
But how do they know (at the check in desk)?

"We had the CS director at Luton explain it to us [& his staff] after they tried to charge us"
That explains a lot

It may have changed since I flew with them, but over 32kg total (with bike option paid) they were charging excess baggage 18 months ago

Turqouise, Black, White, Red, Grey ..
Theres too many colours for it not to clash
The white would work, but I think its the Red that pushes into clashing. Similarly I think it might have worked with the red bits if all the white bits were black (or dark grey)?

After all the money you've thrown at it on high end lightweight bits, why get a heavy bashring?

"entitles you to a total of 32kg of hold luggage (bike +standard luggage), is this correct?"
yes, or at least it was the other summer ago

32kg total (hold) baggage
Anything over that is subject to excess baggage charge. They won't allow anything over 50kg hold baggage regardless
Bike bag is allowed to be upto 32kg
(I belive other bags are subject to 20kg maximum)

For eg
If you had one bike box (eg 23kg) and one hold bag (eg 9kg) you would just be within gthe maximum
When selecting number of hold bags you would select 1 in this instance, and tick the bike sprts allowance option also

"Whats a 64BCD? Its a long cage mech"
A 64mm Bolt Circle Diameter for granny rings
Middle ring position is a 104mm Bolt Circle Diameter

Shorten the chain so it goes round the 2 biggest rings + 1 pair of links and the long cage mech will work. It'll be more in tension than a short cage mech, spending no time in the slacker end of its range of tensioning. If it becomes a problem you can buy a short cage mech later

"one of these"
That lower roller would only really help with stopping the chain coming off under back pedalling, or if the chain is going to be jumping up and down ridiculously
A top guide (MRP 1x, Rohloff etc) will guarantee the chain won't come off under normal pedalling, but with an inner and outer guide ring you should be alright for normal riding. Having an inner guide ring should help with back pedalling too
A lot of people use a bash ring and an Ngear jump stop to do a similar job.

"Scared to ditch the granny ring"]
Don't be, unless you plan to ride the bike up really steep (sloppy) hills all day long.

I found conti 1.75"(?) – 2.5" tubes second only to bontrager 1.75"-2.35" in crapness at resisting pinch punctures. 2.5" rating is a joke (as is the 2.35")
I find specialized 1.5"-2.2" far better, though Raleigh (what merlin sell) 1.5"(?)-2.125" better still as they are thicker and inflate bigger (to fit much bigger than 2.125" tyres)

What fork does you mkIII trail current have?
If a QR 140mm Fox 32 then you'll be lengthening your fork by about 34mm

apart from risking ripping the not strong enough head tube off, its not really the 1.5ish degree slacker head angle that'll be the problem. Its slackeningin everything else off so much more too. A longer travel bike designed for the 160mm bike might have a slacker head angle, but the rest of the bike is designed to handle around it
A slacker seat tube will force you're seated weight further over the rear wheel, and as you'll use your saddle as a sort of reference point for your thighs/kness when stood descending, you'll naturally be positioned further back, more so if you stick a shorter stem on to try and speed the steering up a little. If you shift the saddle forward to compensate then you're shortening the shortened (from propping the front end up) effective top tube length further

Your bottom bracket height will suffer badly too, raising your centre of gravity ablve the bike lots, reducing the bikes handling abilities in corners. You could run lots more sag to emulate the BB height eith the 140mm fork, but you'll be bottoming the shock out more easily (the lower pressure and having more wieght distributuon on the rear wheel from the propped up front end) on a bike with a much more capable fork up front
To keep up with the capability of the 160mm fork, you'll probably want to put some fatter tyres on the bike too, lifting the bottom bracket height further.

The effective chainstay length will be shortened, putting your weight nearer to the rear axle (made worse by the slacker seat angle, perhaps more sagged shock) making it harder to get a decent weight distribution to go uphill

The horizontal distance between bottom brakcet centre and handlebar position (is that front centre?) will be shorter which makes pedalling harder, even with a decent effective top tube length, it'll feel wierd having the pedals so far forward in relation to saddle position

If the bike was designed to be able to run a bigger fork, then chances are they'll have designed around it to some extent, if not then probably not. Depends on the bike design, the bikes frame size, (and riding) as to how well it will work

When brant was testing the ragley mmmbop there were some nice pics on here of one in green with a lot of white parts (as well as black), it looked really good. Not sure where to find it now though

EDIT: found it:

If you plan on riding up any hills at all then you saddle looks like it wants bringing forward a fair bit, though I assume its set up for DH only at the moment

How (and why) is the seattube custom?

I thought those things were meant for vertical geared dropout frames with no IS disc mounts, not track ends

"why is it that all Specialized 'Body Geometry' stuff somehow fails to ever fit my body so…?"

Maybe your using the wrong size? Theres 2 or 3 different sit bone spacing sizes for each saddle they make. If your sit bones are an extreme spacing for eg and you've only ever tried the 'average' size then of course you won't get on.
Go into a specialized dealer and get measured

I didn't get on with an SDG Bel-Air Ti, too narrow and 'pointy'. Lacking in width over enough of its length. For hovering over the saddle descending though I think they are a bit more out the way than some others
I get on with specialized though
WTB Speed Vs are okay, but are bum-numingly wide for any length of sat down riding

Pike @ 140mm Axle-Crown Hieght is 518mm
Fox 36 @ 160mm Axle-Crown Hieght is 545mm

So

Pike @ 95mm Axle-Crown Hieght will be 473mm
Fox 36 Talas @ 100mm Axle-Crown Hieght will be 485mm

So 12mm higher

Specialized UK sercied mine. Though mine is a Specialized shock as well as the brain, nothing to do with fox

"Deffo no 29er circus bikes"
How about a hard riding 29er bike then? Not all 29ers are rigid forked Singlespeeds. Intense are prototyping a DH bike, Niner offer a 6" FS (limited to a 140mm, 20mm, Manitou 29er fork), as well as a number of companies offering 5" 29er hardtail framesets ..

"Are they much smaller than high roller 2.35s?? Or Ardents?? "
Same carcass as 2.35" High Rollers, which are only slightly bigger than a 2.1" Kenda (Nevegal). Along with Ignitors and LarsenTTs (both avail. in 2.35" are older tread designs

Ardents (Along with Advantages and Crossmarks) are newer treads and have much larger carcasses for the stated volume.
A 2.25" Advantage/Ardent/Crossmark is about the same size volume as a 2.5" High Roller/Minion. (Both being slightly smaller than a 2.35" Kenda Nevegal for eg)

The volumes are the same for double (wire) and single (wire) ply (and (single) kevlar folding)

Why do you have to have carbon eastons? Or is that to get upto width?

If you could live with 685mm, then EA70s (265g for 31.8mm, 250g for 25.4mm) are around £40 (if you're going lower you won't neccesserily need as much width)

Bontrager do some 710mm aluminium bars for 265g (31.8mm). Might be called rhythms? Bontrager (Race Lite = 31.8mm?) stems are pretty cheap and I think lighter than Thomson X4s (better check that though). Come in a range of rises too

The best way is to check all the manufacturers websites and see what width bars their ranges cover, what weight they come up as and check elsewhere as to how much they'll set you back

Do you have a link to the original study? Or was it actually published on mtbr?

Why DH wide bars on an XC race bike?
Do you commute offroad?

I think it is the angle of the photo tbh
The bash ring and the small looking shock only make the BB height look taller

The bars look very low compared with the saddle height, as a singlespeed bike I'd have thought you want them nice and high for cranking up the steeper hills. A medium rise (long) stem and some riser bars would be what I'd add
The current flat bars look like they're drooping down a bit, as if they could do with rolling forward a bit

The pink pedals and headset don't really go with the bike IMO (especially with a brown saddle), on the plus side they do go well with the room ..

"too much?"
Yes too much brown, take the chain/seatstay protectors off and it'll look alright

Is that nicolai supposed to have a 160mm fork on, it looks really propped up in that picture. Gold (blocky) stem and bars look vile IMO

Thick gloves? Does that not tell you it really isn't shorts weather?

It sort of goes with the brown, but I'd leave it at that
A gold front rotor wouldn't go so well with the black fork and silver calipers I don't think

Gold pedals would be a no no I reckon

If I'm doing a full clean, I'll take it off and scrub it with the brush on the end of the hosepipe ..
If I'm not getting bored of cleaning then I might use a casette/drivetrain brush to give it a bit of scrub

Ardent front, advantage rear? Eh?

Does the shim insert into the frame with the seatpost? Or does only the seatpost go into the frame?

I read somewhere that ghetto tubeless doesn't work well (safely) at higher pressures is all

Get some carbon friendly grease (other grease can cause the carbon to delaminate apparantly). Pace do one. Its pretty pricey at about £9 for a tiny pot, but you won't use much so it'll last ages

I got mine from 18 bikes in hope

My carbon post had lost its outer shiney layer and was starting to become difficult to raise/lower. The grease seems to fill in the gaps, its now easy to raise/lower and it hides the scratches. I just add a little more if it starts to become a little sticky in the frame

No tubeless rimstrip, I was hoping to use them tubed for now. There is a thick(ish) normal rimstrip sort of stopping it from dropping into the middle though

Right, washing up liquid, I'll give it a try, should I try watered down or neat?

So probably not rideable then? ..

One of the coils hasn't snapped has it? Not quite sure how it would affect it exaclty, but just something to rule out

It should be a standard IS mount (I'm assuming it is)? So whatever caliper would run with a 160mm rotor normally I'd imagine

How new is it? How long is the shimano warranty? If a seals gone then surely your shop should be able to get it repaired on warranty, ie free of charge?

Just a a suggestion,

How about the 20mm adjustable fork goes on the FS and get the 130mm Recon spacered down to 100, 115 or 120mm? Or run loads of sag on the Kinesis?
You friend might notice more difference with a pike on the full suss than on the hardtail?

I suppose singletrack did run a 140mm 20mm fork (was it a Thor?) on a Virsa for a while recently?

I bought an SDG Bel Air after only ever seeing postive reviews

I didn't get on with it. Too narrow and pointy. I think its a little better at dealing with stood descending though (its slightly more out the way for thigh rub), currently on my 'play bike'

I get on with Specialized saddles way better (after having my sit bones measured with the memory foam
The format (designed to be easier to move behind), is a bit easier to move around, but is a bit too hard and small (they've removed the back comfy part of the saddle) for all day rides really

WTB Speed V is too big

Slimmed down route of suggestions (Again not suggesting this as a whole (though might be good) but as a way to include stuff)
took Hollins X out (usually quite sloppy), put in Rushop Edge
Included Cave Dale AND pindale (so take ~1mile off (And half a climb) if you only did 1
Roman Road instead of Hope Brink
Short cut Push(/ride) up after the beast (the beast could be an optional extra near the end)
http://www.bikehike.co.uk/mapview.php?id=29963
ABout 17.5miles with one of Cavedale or Pindale. 18.5 with both

I'll stop now. Extra route posting is just confusing things