Thanks again for the additional posts.

It's agreed you would need strong parts.

I can't estimate if you could take a P/S engine and just lower the compression, you probably would lose
all the bottom end torque if you kept the same cam duration. Is it accurate to say that cam duration/timing
is what primarily determines RPM range ?
Also, it could be the ignition advance curve for such an engine would look quite unusual, but maybe not.
If they flame front burn rate increased with increasing RPM, maybe due to the violent mixture motion,
the advance curve wouldn't be too weird.
So if you had breathing and combustion, it could work.