Sawdust,I'd go with the 55AX,you can always throttle back.I didn't use the provided motor mount(or any of the other hardware or hinges) so I didn't have any problems fitting the 55.The 55 will fit in the kit motor mount if you file it to fit around the 55's crankcase.This airplane doesn't care about wind.This is a pretty good arf,the hardware and covering sucks,but overall it's ok.It does fly like it's on rails,and it does scream with the 55 on it,so I'm good with it.I would make it a taildragger if you fly from a rough field like I do.Have fun.

Jim