Wrenwright,try an APC 5.7x3 prop.You will like this particular prop on the Dragon Fly.I have two of these engines and have experimented extensively over the years with different size props.This is the prop that has given me the best "all around" performance.As was mentioned earlier,the Dragon Fly engine is not a powerhouse like a Big Mig .061 a Tee Dee .049 or even a Black Widow but it does have a fairly descent throttle control(for a reed type engine) and a good "stunt" type fuel tank.Try to keep the R.P.M's up a bit with this one as it doesn't like to be bogged down with high pitch or larger diameter props.If your looking for more power out of this engine,try running a Tee Dee .049 glow plug which has a higher compression rate.Easy "screw on" performance improvement.