I wouldn't put more than a Magnum .60 four stroke. Even that is an over kill. Flew mine with a TT .46, seemed a waste when I rarly went to full throttle, even on takeoff. Switched to a plain old K&B .40 and put the .46 on a WM T-34. If I were to do it over again I would put a .52 four stroke. The .40 does fine but would like more pull on hot days. Typically it doesn't climb well on a hot summer day till it gets over the ground, too much hot air over the asphalt I suppose.