I have been running the xx1 crank with a 32 teeth ring and standard cassette on rear with clutch derailleur on a 650b. In terms of weight it probably shed close to 500g over the 2x10 setup all things factored in. I am concentrating mostly on XCO and so far i'm pretty happy with the setup. I think an extra 42 on the rear cassette would be perfect (just couldn't justify replacing hub etc). I do miss my granny gears on some of the more technical steep climbs, it's not too much of an issue with the XCO courses though as the climbs are generally short. I will be trying to source a 30 front if they exist as this would probably be a good spread for XCO.
