La 15s are run in Clown racing. They can howl. Also they get put on bladder with the venturi removed. Run in CL combat. I believe they are the required power for at least one class of RC Combat. Replace the remote needle with a threw the venturi needle. Add nitro. LA25s can be run sweet. I have seen many ARF Flite Streaks doing no fuss no muss patterns powered by an LA25. I think the prop is a 9x4, usually. Through the venturi needle, best way to go. If you are inclined, up the nitro some, and let it howl. Fp 15s and 25s seem to have even a bit more guts. We see FP15s topping out at over 20,000. Fp 25s. Near that. Both run fine on bladder with the venturi popped out. Screamers. Very entertaining. Cheap considering what they will do. So far no broken cranks. Even tho folks are working at it. In many ways these engines are superior in speed limit combat to the high priced, hard to get, dedicated combat engines. The crank bushing will take a beating, going into the ground, without needing a bearing redo.