Don't have the plane; but a friend did back in the 80s. He flew his with an O.S. 40 and it had plenty of power. I'm not saying your over powering yours, only that he had plenty. He flew the heck out of his and always said flying it was akin to putting on an old pair of shoes; "comfortable".

I always ran 11X7s on my OS .60 "Blackhead" This was a good all around prop used on a sport engine.