I've seen a twist or two fly, and this plane is not in the same class. It's meant for 3D, not exactly what the Twist does well at. Motor mount holes are slotted in the mounts to work with most engines in the size range called for. My 61 is about 20 years old, but flies the plane great, and I need no more power. I guess my question to you is how well can your 51 turn a 12-6 prop? The model weighs 6 pounds with no added weight. The guys with the 82's are having trouble getting the cg back. Mine is actually a little tail heavy, but flies great like that. Besides that, I'm not familiar with Como engines. If it runs good upright and sideways, it should run fine inverted. All I do is make sure not to over lean by checking the needle setting with the nose held vertically. This tends to make it seem a little rich on the ground, but clears up in the air.