I don't worry too much about getting the absolute most HP or speed from a model airplane engine. More often I am trying to achieve a combination of power/thrust/airspeed for solid control response and good vertical performance on the particular model. This leads to using slower turning, larger diameter props. I have tried some 4 strokes and prefer 2 strokes with tuned exhaust systems allowing the adjustments that are sometimes needed to get this type of performance. I have recently acquired a few liners for ST 90s and plan to do some experimenting with the porting, piping and propping of my engines.

Terry in LP