ORIGINAL: hogflyer
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
The 14x6 is even outside the suggestions given by OS. 13x7 is the biggest in the manual. I can't imagine how bogged down the engine was.