All of the info I have received seems to indicate that 4 stroke engines run well inverted. Before there were glow plugs we used to run engines on ignition inverted with no problems. Perhaps it was because the ingnition plugs were hotter whenever they fired. Flooding will always be a problem if the engine is inverted. We hand started everything and only seemed to get bit when advancing the spark. Most of the pilots I know turn their aircraft upside down to start. As I observe it seems to be a very dangerous proposition to turn the model back to upright with a howling or even idling engine. Should be at least a two person operation.