Yup, think of it this way. Smooth burning in the combustion chamber is just as important on these tiny little engines as it is in a car engine. If we're turning a small prop at a very high rpm, we have to start the ignition process earlier so that the point of maximum cylinder pressure occurs at just the right point in the piston's movement for max. power. The ignition of the fuel/air mixture is controlled by (among other factors) the compression pressure so more compression = earlier ignition timing.
Conversely, big lumber needs the ignition point to occur much later or the point of max. cyl pressure occurs too early and is wasted trying to push the piston back down before it gets to TDC. That usually causes detonation and broken parts as well.
Me? I have much better luck under-compressing my Cox engines and giving up a little top end power. They smile at me when I run them.
