Well the results are in. Even after boring out the exhaust, which did get me about 300-400 more RPM, the engine is still a dog. It could barley pull my HOR around. It ended up doing a nasty snap roll and buried inself in the dirt. This probably was do to the construction of the airplane, but either way the AP was grosly under-powered. So anyway, I'll be repairing the old HOR, and installing the OS LA .15. Hopefully I will get decent performance from this setup without having to result to 30% nitro. From the looks of the other Hor's at the field this won't be a problem. So I'll say it again, anyone want a slightly used (and abused) AP .15 Yellowjacket? $30 or highest bidder.