RE: AP .15 any good?
I have two and a friends have a couple. They require a long break-in, just like a norvel does, before they run well. They are much smaller than OS, Magnum, and similar .15s. The muffler completes the compact design but also requires more room between the engine and firewall. My experience doesn't lead me to believe it is much more or less powerful than the average .15. It should be noted that since it is a rear exhaust it could be fitted with a tuned pipe like many pattern planes had.