Thanks for the responses so far. One of the reasons I built this plane was because of all the stories I have heard about how easily it tipstalls, should make for a fun snap roll, spin type airplane. I wanted the classic looks of a high wing airplane without totally falling asleep while flying it.
I think I will stay with my original plan of the OS.46fx, although I really do like the sound of the 4 stroke.....if I had a 70 sized 4 stroke sitting at home I would have not had to ask this question as it would have been the engine of choice, but I am a bit concerned about under powering the plane with the Saito .56...