While I don't have a "Fun Fly" type of plane in my fleet I have seen the light when it comes to 4 strokes. My first aerobatic plane was a GP Cap 232. Origionally I had a .46 FX up front. In the search for more power I added a .70 Surpass II. What a different plane. No longer did I have to wait for the plane to pick up speed after a violent maneuver. I simply add power and the plane almost instantly regained all of its speed. I went from an 11X5 prop on the .46 to a 13X6 on the 70 and it greatly improves the low speed handling of the plane. There is so much more thrust that it really brought the plane to life. Additionally, with the lower speed to the prop there is more effeciency created. As props start reaching the 11-12000 RPM mark there performance starts to degrade. I used to be able to rip the prop when I did hovering type manuevers. When you hear the prop ripping it is actually much like cavitation on a boat prop. At this point the propeller is exceeding its ability to effeciently provide thrust. I have yet to come across this with a 4-stoke.

To each his own, but don't knock a 4 stoke until you tried one.

Sure they are a little more expencive but have found them as much if not more reliable than my OS .46 (Flawless running engine). Oh yea, and one more thing, they are way more fuel effecient and less messy!

Good Luck, Phil (Mesa, AZ)