I have the exact same plane....started off with the 81" wing and a sideways mounted OS.46AX with pitts muffler. It flew the plane just fine and ran like a champ.

But

3 years ago, I clipped the wing down to 67"for more sporty flying and 1 1/2 years ago put in a Saito 65 4 popper as that made this plane truly sound great. The Saito 65 does have good power but I might swap it out for a Saito 82 that is sitting on the shelf just to give it that extra ooommmppphhh.