CL fliers use inverted engines all the time without issues, although they are confined to circles and no throttle. What I have found in CL (don't do that any more, but have a couple of friends that are among the best in the nation) is that they are very precise with every thing they do, especially in their engines and their tank set up in relation to engine position, something we R/C fliers need to pay a little more attention to perhaps. I also think that part of this comes from the fact that the C/L guys build their airplanes from kits or scratch (these two build from scratch) and we build ARF'S.

I've found that as critical as tank height is, it is much more critical with the engine inverted. If it is a little high, the engine is going to flood, at least that's been my experience with a Seagull PC-9. Got the tank positioned properly, leaned the engines high speed needle and low speed needle and never had a problem with the Irvine engine in the nose after that. It was a great flying model, and the engine was absolutely right on every time I flew it. I don't recall ever having a flame out after getting the tank positioned correctly. What I don't understand is why a model that is built for an inverted engine would have that flaw engineered and manufactured into the model to begin with, of course, this was from one of the early runs on this model. I have another waiting to be put together and they may have corrected that little problem, which was the only problem I ever had with it.

You've probably checked your fuel lines for the possibility that one has a pin hole in it (had that issue with the OS 160 with a Perry Pump in my GBY, with similar results), including the fuel lines in the tank and that the weighted pick-up line is not hung in the front of the tank. If you have not confirmed that, it would be something you might consider before you reposition the engine and or tank.

You might also consider a Perry Pump or Klein Regulator (if you have room) if the tank is too high or too low and you cannot reposition the tank without a major over hall.

"Experience is a hard teacher. She always gives the test first and the lesson some time later!"