Robert,
Now why didn't I think of that?
Reminds me of my first misadventure with a Pee Wee powered free flight. Built a Goldberg Ranger 30, installed a brand new Cox Pee Wee .020 engine, trimmed it for a perfect gliding circle, test ran the engine to check tank capacity, added what I estimated was enough fuel for a ten second engine run, and launched.
You guessed it! The engine offset was exactly enough to offset my carefully adjusted glide trim, and my tank capacity check was a little off, in fact WAY WAY off. The beautiful little Ranger flew in a perfectly straight line, climbing until it was just a speck in the sky, with the engine still screaming! It went out over the Atlantic ocean, never to be seen again.
That was fifty years ago, and I never built another free flight airplane!
Bill