If you are going to use an engine to power a mini ultra stik, a .049 is way too small. This plane has a 42 inch wingspan. I would guess at least a .10 or better yet a .15. This plane was designed for electric power so you are going to be in for a lot of modifying and fuel proofing. Leave it electric and use a e-flite Park 480 brushless outrunner with 2100 mAh 3s lipo batterypack. You won't regret it.