some do use egt gauges to tue, but more than just timing. 2 reasons the ignition timing is affected so dramatically different on a 2 stroke. charge timing, and pipe timing. on your rice rocket, the charge timing is controlled directly at the the chamber, maintaining a relatively small amount of delay, which can be changed with cam timing and different porting shapes. on a 2 stroke, the piston must pump the air down to the transfers, and back up into the cylinder. for this reason, the delay increases as the rpm's increase affecting the amount of charge. so, when you are ported, and they talk about port timings, think of it as the 2stroke camshaft. the higher the ports, the longer the charge timing at higher rpm's, but lower compression ratio. there is a hell of a lot more to porting than that, but that's kind of an idea about it. the second thing is the pipe. on a 4 stroke, exhaust is pretty much just an exit strategy, even though tuning the right back pressure effects power. on a 2 stroke, the shape and length determins the timing of a return pulse to back charge into the chamber, raising the compression. higher compression will cause the charge to burn quicker. alot of spark advance at higher rpms is not only dangerous for heat reasons, but short circuts the full potential of the explosion by being at full force before the piston can even be pushed back downward.
this is just my 2 cents. i'm sure someone will have a different idea about it, or part of it. :thumbsup: