RE: AP .15 any good?
I have had two of these and this is my experience. The only plane I had these installed in was a Randy Randolph Chips. The power for this was excellent and competed equally with any other 15 powered Chips so I would say that the AP 15 is as powerful as any other .15.
On the down side, the first engine was returned as the backplate did not stop the con rod backing off the crank pin and wearing prematurely due to the decreased bearing surface. Fair dues to Hobby Lobby they replaced the engine with no problem. Unfortunately the second engine went the same way. Be warned - check the back plate fit.
The second was replaced with a Magnum .15. With the comment that this was more powerful than the AP. I havn't run the Magnum yet.