Rclement...I started off with an O.S .46FX in my 1st T _ _ _ T, and it flew just fine. It is enough power to fly it comfortably, but it, in my humble opinion, lacked real power. Then DownTrodden convinced me to switched to a .61FX, and till today I still thank him for that!!It was a day and night difference!I love to fly by low and slow, so I can have a good look at the plane, but if I hit full throttle, she goes vertical unlimited!!I love that engine!!It is a tight fit, but heck, once it is mounted, you're set!!If you can effort it, I can strongly recommend you considering this engine!