what is the wing area on the .60 sized top flite? Once you have that you can refer to the rules on the SAM site as listed in post #42.

As for Nitro on a 55 AX, I really do not know what will work for it. It has been my experience that you really do not normally want to put more than 20-25% nitro in a 2 stroke. There are a few 2 stroke guys that may chime in if they have the experience with said motor. I fly mainly YS 4 strokes and as such do not have much experience with the 2 cycle motors.

Jimmy Skids