My Twist goes straight up with a Thunder Tiger .46 Pro. The only drawback is I had to add a bunch of weight to the nose to get it to balance out in the proper range. If I chose a different engine I would pick something that will allow it to balance without the added weight and have the benefit of added power. A .61 two-stroke might be nice if it would fit in the tight nose of this plane. I have considered a Webra .61 but the real problem would be getting the engine mount to fit in the limited space which probably makes a four-stroke an easier fit. The problem is this plane really doesn't need the extra power. I detected a small amount of flutter on mine when I opened it up. The culprit may be the stock pushrods which are a bit too flexible. Be sure if you overpower this plane that you are using it for vertical ability and not to go screaming across the sky. Losing your elevator to flutter would surely cut the day short in a bad way!