drvcrash - a 63fz would be way too much power for this plane. In my opinion a O.S. 52 or similar Saito would be absolutely the best match. I had the 32sx from another plane. Had I not had that lump already, I would've certainly put in a 52 O.S. or 56 Saito. It deserves four stroke sound! The Y.S. 63, although a great engine, is not only too powerful (not all people have that in their vocabulary) but also too thirsty. With the Y.S. 63 you will probably only get 8 minutes or less at full throttle. I know because my WM Rambler 30 ran out of gas after 8 minutes of flying. I had limited it to only 70% throttle because it was torquing the plane way too much. In fact I had to couple some aileron to throttle even with only half throttle in order to have it stay level throughout the throttle range. So 8 minutes at 70% throttle (admittedly running rich) isn't great run time in my book.

My 2 cents? Don't over do it. Keep it within the envelope and the plane will be a blast to fly.