I liked this kit so much back in the 70's that I built 7 of them. Back then a big .60 was about the max power we used and did fine on them. Do pay attention the the relative incidence of the wings. All mine flew best when the upper wing had about 1.5 degrees less incidence than the lower wing. Also required about 2 to 3 degrees right and down thrust. If I were building one now, I'd put a 90 to 1.20 4 stroke in it, should be a ball. Right now I'm about finished with the giant Aeromaster, putting 72cc Quadra in it.