As Yel914 said, side mount the engine and build a cowl and I think a tank hatch is a must. Mounting engine on its side lines up the carb and tank center line for more consistent fuel draw and this is important. I have built one SE with larger rudder but found it doesn't really need it unless you are into knife edge flight. With a larger engine it will knife edge anyway. You may think the SE can't handle a larger motor but it can easily handle a Tower 75 if set up correctly. I have used many engines on this plane and this plane can peform with all. Engines I have used so far-- OS46, 61 Saito 65,80,91 Tower Hobbies 75. This plane is a great sport flyer and can handle fast of slow speeds with ease, ever with the 75. I think the Saito 82 would be a great engine for the SE. One other thing I would change is a taller landing gear from TNT landing gear. This allows larger lower pitched props.