One of my former students was flying a 14 X 6 on his OS .55 AX at the recommendation of the LHS. It was on a GP Cherokee and the performance was dismal. It could barely get out of its own way going down hill with a tail wind and a .46 powered version of the same plane flew circles around it. I told him I used to fly 11 X 7-1/2 on pattern planes and to try and 11 X 7. Once we put the 11 X 7 on, that .55 AX woke up and proved to be the right combination for that particular plane.

Hogflyer