OK. The Saito 180 is a GREAT engine, but Horizon doesn't have it right when they say to use a 16X8 prop. That is too small for that engine. No 4 stroke should go above 10,000 on the ground, regardless of what the instructions say. They will gain RPM in the air, and you will wear it out too fast. YS engines are the only exception. Some of the smaller ones are built to rev up higher. A 16X10 prop is better, but something like a 17X6 is good. The only problem is the 17X6 is hard to find, but I have seen them. I saw a Saito 180 on a Sig Extra and with the 16X10 it was a rocket on vertical, and the engine wasn't revving up over 10 on the ground. Another good choice is the OS 160 2 stroke. It's got just as much, if not more power than the 180. It sounds almost like a gas engine too.