well, have taken it for it's first proper ride now and have to give it a big thumbs up, it is flippin' quick and very playful!
For the first 20mins or so I was thinking it was feeling a bit short and could have done with an extra inch in the top tube/on the wheelbase but as soon as I got it into the twisty rooty tight steep stuff we have here it was absolutely spot on, it is really really nimble and the centre of gravity is really low, it feels like the entire weight of the bike is in the bottom bracket, it's really really planted and very very stable in the air.
Standover height is huge, works really well when steering with your knees in turns and a lot more leeway for bailing on steeper bits!
There's a little more flex in the front end than the old Schwinn frame but it actually works really well, especially with a big bolt through fork, if you smack it through a rock garden at full tilt the fork stays on line and the back kind of wiggles it's way through a bit instead of getting deflected off, makes it a very smooth ride and it carries the speed really well and it's not enough flex that it loses it's line, just enough.
Probably going to put an extra 10mm travel back into the forks and wind the trunnion up a little to take the BB up 1/2 inch or so as I was smacking my pedals a bit too often, but then I'm running 175 cranks on it and I normally use 170s so crank swap might be in order.
It seems to have kept all the good traits of the backend too, soaks up more things than it should for the amount of travel, has ludicrous amounts of grip when peddling back up loose and rooty climbs too, and is totally planted on the way down too, and will still slide the back end out in a controlled way if you weight the outside pedal and give it a little kick so very happy there, pivots have moved slightly compared to the old frame and consequently it ramps up a tiny bit more towards the end of the travel than it used.
Has come in at a smidge over 31 lbs, which is not bad and only about 1/2 lb heaver than the old Schwinn. Scope to lose some of that too as It has a hefty old Mavic 325 (700g!) rim on the front and the 2.4 Advantage is not a light tyre but I'm happy with the weight anyway, especially given where it's CofG is it's not that noticeable handling wise.