I've got to go along with Ed. I have a friend that used emery paper on a flat surface and ground down (slightly) the cylinder top.This raised the compression slightly and the engine ran significantly stronger. My opinion is use it on something like a Curtis Robin type model. Too bad, they were kind of a cute little engine, but they would make a better anchor for a row-boat as their power to weight ratio was really awful. Ok, next time I won't hold back.
Best of luck, Mike