I worked on this question recently. You are right. I wanted to use the twin plug heads. No go. The pistons? The squish band is to narrow to fit in the combustion chamber on the head. Easy fix turn the piston dome diameter down an blend in. Valve clearance is o.k.
The other problem with piston, the flame front does not propagate over the top causing detonate or pinging under wide open throttle. It can't be timed out. Retarting the ignition timing affects idle.
I got 230 psi compression. I got pinging I got more h.p. Using the stock map. Had a fuel controller installed, but removed it.
2003 hydro motor. Lifters seem to hold up to the high compression. Starter turns engine over good. Some times on a cold start and lifters are not pumped up, I can hear a valve slam shut.
I ride the bike hard, disregard the occasional pinging. I have an extra engine fully rebuilt if thing go wrong.