18 X 8 APC but think I might switch to a 16 X 8

This was plenty of engine for a little Bipe . Def requires a new set of skills to fly but its a blast.

Keep an eye on those little 440 bolts that hold the metal wing connector brackets to the fuse. They loosened up from vibration when I was breaking in the engine. The are a royal pain in the ***** to tighten.