Although I usually have a 5km ride before I get onto trails I'm wondering whether I should go 2×9.
Am I likely to save much weight and is it worthwhile?. I do have an XT crank that I'm probably not using this winter so could use this if required. Is it simply a question of removing the big ring and stopping the front mech from moving too far out?

I did the adjusment on a triple mech for middle and outer rings when I junked my granny ring. I found the mech difficult to budge and double made it work properly and smoothly.

It can stress the shifter but in your case there will be less shifter movement.

You won't save much weight no, it's only really advantageous if you're prone to clouting your big ring on things, if you're not I wouldn't bother.

If you are then get a bash ring and yes, adjust your front mech so it won't overshift.

significantly easier to adjust the front mech for only two rings
wider use of the cassette.

if you go 22/36 up front you only lose the gears 44/11 & 44/12

My thread below covers it all I reckon. I'd certainly not go back to a triple now.

http://www.singletrackworld.com/forum/topic/experiences-from-other-2×9-and-no-bashring-users

I've just ridden Welsh trails (Whites, Brechfa etc) with 1 x 9 and had no probs.

I am probably returning to SS now but it was worth adding the rear gears for a weekend like Wales where I knew I wanted some extra help going up and down.

I've run 2×9 for the past couple of years, ever since I clouted £35 worth of big chainring on a rock.

I use a 36T middle ring which covers most of my gearing requirements, my bike isn't the slickest rolling, so the top three ratios are as high as she'll easily go.

Works for me.