The sig hawg Bipe is a great first bi plane, but it wont fly with a 40. Most 40 size bipes I've flown are a bit squirly and a sharp eye is needed to fly it well. I like the larger planes, as they are more forgiving and I think fly much better. Building is a bipe is always a pain, but once finished it will be your favorite plane. The Sig has been one of my easiest bipes to build. Nothing like seeing one flat spin. Very gentle or wild. You chose. I have a 91 4 stoke in mine and wouldn't mind have a 100 or 120. Wish I had a GP 40 size bipe. Dont remember what it is called, but it looks sharp. Once again it is a kit though.