In my opinion the 65 four stroke will not have enough guts for a Hog Bipe.
Most of the people seem to use 91 class four strokes with a few Saito 82's and 100's thrown in for good measure.

edit here..........
I just reread your post, if the plane came with a 65 mounted in it was it ever flown before you got became the owner ?
If it was then obviously the 65 can fly the plane.

I still think the plane "needs" a 91 class four stroke though.