RE: Best engine for a 4*60
I have built many of these planes (all kit built) and tried a few engines, OS .61fsr, ST S-.61 abc, Enya .90 four stroke, OS .91 surpass.
My favorite was the .91 surpass, as it had the best balance of power, throttle responce, and long run time on a 14oz tank. The Enya was a very close second. The other two engines were okay and had plenty of power, just not as much fun.
The 4*60 is a rather draggy design and the fourstroke seems to less bothered by it because part throttle power and torque is IMO stronger than that of the twostrokes.