Fastest trainer I've seen (that hadn't been totally rebuilt), An Alpha 40 with an APC 10x7 and a 2.75" spinner (I think, a spinner big enough to almost reach the fuse sides, it really helps smooth out the airflow and increase airspeed). Anyway, the Alpha is pretty sporty with that setup.

I have an APC 11x5 on the Evolution TPS engine I have in my LT-40 beater plane. I also took the baffle out of the muffler for some extra power at the cost of some noise. (I got the engine from an ex-student who was going all big stuff. The engine had already been seroiusly abused before I got it. Still runs great)