On the throttle overrun mine has a tendency to back the auto adjuster cross slide off leading to a kangarooing with the noise of a hundred midgets going at it with anvil and hammer !!!!
Usually occurs when pulling away with too few revs in second gear.
The Allen bolt is 6mm and although the cap it's screwed into has a very slender wall thickness there is enough meat for about three full threads.
There is no load on the screw as such it simply stops the cross slide running back and slacking the chain.
Just have to remember to adjust it when the chain is in the correct tension!
Personally i would rather not fit one of those bland and repugnant APE tensioners and i saved £40 into the bargain.
Runs fine on a <>200BHP Turbo J so its probably OK for my old nail.
AL