Unfotunatly, in the 4 strokes it is WAY low. They are designed to run in the summer, with partially clogged fins, on cheap 87 octane gas and not ping and knock to death. We might have great cooling, 93 octane gas and the ability to run much higher CR, but there isn't much market for hopping up these engines and no high CR pistons out there. The 4 strokes also have either a geartrain or belt that makes machining down the cyl base an unreasonable option.