How to shim the inner chaincase ?

I have dismantled my primary and found that there is heavy scoring of the back of the inner chaincase where it has rubbed against the drive chain around the gearbox sprocket. Can anyone give me the correct thickness of the spacer on the centre stud ? Also what is the correct way to shim this up so all is in line as I don't want to overstress the 3 front mount bolts as the threads already look a little delicate.

The shims are "as required". I think I ended up with about .032 worth. You need to measure the gap between the hex stud and chaincase with a feeler gage with a gasket in place on the crankcase/chaincase joint just as it will be when assembled.

One thing that happens to Commandos is the 3 rear engine mounting bolts wear oblong holes in the aluminum cases and the engine twists to the left, which puts the chaincase against the swingarm pivot. If you find that even with the correct shim in place you still have no clearance there, try loosening the 3 thru bolts and see if the motor moves to the right. That's a sign of the crankcase holes being worn.