I have one with an OS 65 LA and a 12 x 6 prop.

If you put an engine of that size on this plane, you want to think about changing the decalage (sp?) (i.e., the relative angle of the wing to the horizontal stabilizer). On my plane we see a lot of ballooning whenever power is added. If you raise the rear edge of the wing, or the front edge of the horizontal stab, you won't see the same effect on yours (I raised the wing trailing edge about 1/8th inch and it helped).