Loved the video. That terrain is exactly what we ride in up here. Except there is no fun sand but lots of mud, swamps and slimy hill climbs. Maybe I should move.
I haven't done the 350 sprocket modification yet but I have a bike that is reaching the limits of the adjusters, so I will have to do one soon.
Cliff has a bike that is so desperately in need of a sprocket, that the bike practically begs and pleads for maintenance when you push it backwards. The sprocket teeth are so bent over that the bike pops as the chain gets caught in the sprocket when it is reversing. We have begun to call Cliff "Captain Hook" when he rides this bike.
We have thus far avoided fixing the issue by not pushing that bike backwards so much.
Still, it is going to have to be dealt with soon. Or soonish.