Speaking for myself, I don't know where the threshold is but from what I understand the main safety net for compression is twin plug heads.
When I was able to look at original high compresion RSR pistons it was pretty obvious that he high compression dome pretty much blocked off half the head area from seeing the spark plug.
On the other hand, the wedge shaped Max Moritz style pistons keep the flame path open with the high part of the piston located at the far end instead of in the middle. Obviously not as much compression but more than stock, yet still a margin for detonation safety that a domed piston does not have without the need for twin plug.
Max style JE piston
Original factory 3.0RSR piston
