On the Evo engine, which is a super engine, you remove the prop and the thrust washer/weighted flywheel. That is mounted right behind the prop and it slides off. The normal thrust washer from Evolution costs less than $3. My LHS ordered mine. Slide the thrust washer on the notch, put on your favorite 2 bladed prop, and tighten it all down. Go fly. You will get a lot more power and higher RPMs. I'm using 11x7 props. (Be sure to remove the baffle out of your muffler)

I think I read somewhere that someone tried to fly with both the weighted flywheel and a 2 bladed prop, and barely got the plane around to land. If I remember correctly, it barely had enough power to lumber around once for a landing.

I've owned an OS .46 FX, a TT Pro .46, and the Evo .45 Trainer. The Evo is the best of them by a long shot. It the OS .46 dies soon, and it sounds like it may, there is no question of replacing it with the Evo .46NT.