The .56 is a great match, both in size and power. That's what I have in mine, great performance. A .72 will also fit, and according to tlw, so will the .82. I'll bet his will go out of sight straight up, because my .56 will take it a pretty good way before it loses its oomph.

BTW, a .65 will NOT fit, engine case is too wide at the mount rails, and neither will the older .80 fit.