These small industrial engines are over-engineered and detuned. This is done to make them "idiot proof". They are designed so that the average person can just grab one, throw some gas and about any kind of oil in it, and run it full throttle all day. They often get the cooling fins all filled with grass, dirt, wood chips, whatever, and are run until they quit with no service or kindness, then get a spark plug change and do it all over again. They are designed to do this, and survive!

As such, they respond readily to mods to increase the performance, since they are supplied in a detuned state to begin with. They have a much nicer life in our model airplanes, with adequate cooling, relatively short runs, usually better care, etc. I have had virtually no reliability problems with my converted and modified engines. I have a Homelite 30cc that I run at 9500 rpms, and the boat guys regularly run the same engine over 10,000 rpms! It has been said that "You won't live long enough" to wear out one of these engines in a model airplane given decent care.

All hop up endeavors are best done in "combinations". One modification compliments another. Yes, you could gain performance by just raising the exhaust timing, and yes, the same by just raising the compression. However, a well planned program of mods that addresses all aspects, including carburetion, muffler, port timing, compression, etc. is what really produces good results.

I have noticed no negative aspects of removing the squish band, though doing so in larger engines does impact detonation resistance. An easy way to measure deck height is to insert a piece of 1/8" thick solder into the spark plug hole, bent so that it touches the edge of the cylinder. Then turn the engine over a few times. The piston will flatten the solder and you can then measure it to get your deck height.

Finally, I have heard that leaving the "glow heat" (battery) connected to a glow plug will decrease it's life, but I have no direct experience with this.

Good luck,
AV8TOR