Most people use more power than that, but it really depends on the weight of the plane and the kind of flying you like to do. I saw one fly quite well on a Saito 62, which is less powerful than your engine, but I think that plane was a little lighter than average. If you find your CG is too far back then get a bigger engine for it. It will probably benefit anyway. But if it balances pretty well with the ST 51 then I would try it with that engine and maybe about a 12x4 prop.