RE: Smallest gas engine
I have one in a TF P-47 ARF. Took a lot of fooling with to get it to run reasonably well. Endless twiddling with the carb would not eliminate a "poping at top end. Finally advanced the ignition about 5 degrees (needed a Dremel) and things smoothed out. However, now if the engine is snapped to idle it will die. Flies the plane well when used carefully. Makes 7900 RPM with an APC 15-8.
DJ