Sterling it's not that I want to rip my engine off my airframe or even perform 3D I do however like a little extra power to play with. A nice climb out, maybe 2 or 3 vertical rolls thats fun. But its not just that, power can save a plane. If I overshoot my landing and need to climb out or I have a low level stall extra ponies can save my butt. As for breaking things I have the same concerns as you, that's why inquired about the quantities of servo's in the wing. To me it wasn't the engine in question it was the size and weight of the airframe itself. My madness is really simple but not all that scary. If your thinking of a 120 fs say a ys it will happily turn a 15" or 16" prop as well as a saito 150. The saito 180 will turn a 18-6 at about 8200 to 8800 rpm and provide ample thrust to weight ratio. Now I'm not saying that there isn't enough power to pull the wings of that plane but that's why we have a throttle stick. Wing loading isn't really and issue because by my estimation your making up the extra weight of my engine with dead weight. So the only difference is power. High G loading is a consideration but only if I were pushing the airframe extremely hard and at that point I think flutter would be more of an issue. You don't have to fly full throttle all the time. I would rather fly my saito 180 at 25-75% throttle and have low rpm's low vibration and low noise than have to fly a smaller engine at 75-100% with high rpm. I'm saving on fuel and engine wear. Not to mention I have the extra power when I need it. I'm not knocking smaller engines but If you need to ad weight, maybe it should help you fly and not hinder. Also I think the larger prop will look great and sound fantastic on slow flyby's. As a fellow modeler don't take offense to this I am just explaining my reasoning behind using larger engines vs. smaller. Your caution is appreciated but from what I read this particular application could use a larger engine.