I did increase exhaust timing a little bit by raising the sleeve 0.1mm, though that means I also increased the transfer-port timing as well. I also dropped the total height of the shim stack 0.1mm, down to 0.3mm from 0.4mm. I could drop it further, down to 0.2mm, but that would leave only a single 0.1mm shim between the sleeve and the head since one of the shims is under the sleeve instead of above it.

I agree that increasing compression increases power, especially in the mid RPMs, I've seen that myself on other engines. Not on this one though, for some bizarre reason. I have no doubt that cleaning out the transfer-port channels must've helped somehow, because they were really badly obstructed before. But the effect on the engine's power output appears to have been academic.

Doesn't increasing compression have a negative effect on the top speed of the engine? I read that somewhere but I confess I have no firsthand knowledge to back it up.