A couple of years ago, I helped a visiting gentleman break in a os 55 on a 40 size u-can-do. He said the trick was to have hemostats on the fuel line going to the carb at all times except when the engine was running or the tank was empty. He had several u-can-do's and this one was going on floats. I can say that after 3 tanks, this plane was running real nice. This man had experience with inverted engines and had it adjusted to run that way. I know that the air frame was stock, but don't know if anything else was changed.

David