I have a Four Star 60 that I have used 2 four strokes on, a OS 91 and a Magnum 91. The four stroke and size engine are great. I used to run 14x6 props and have switched to 14x8 props, a little more speed which makes knife edge much better and allows flying at half throttle. I also move the CG way back. I added 2 oz of lead to the tail wheel. This really brought the plane to life and it still flys like a ***** cat, not bad habits. The plane will lomshavac (sp?) , flat spin, hang on the prop and just about anything you could ask of it. Best all around airplane.