Tank height really only affects SIPHONING of fuel when the plane is sitting on the ground with the engine off. Siphoning will make the engine difficult to START or hydrolock the head.

(well in actuallity it COULD affect normal engine running, but this would only occur in the rather unusual case where the tank was significantly away from the engine... e.g. over 10" or so )....

Otherwise our engines would die out whenever the plane goes nose up or nose down.... where the fuel level is a good 6 to 18" BELOW or above the carb depending upon the plane

Any 2 or 4 stroke glow engine will run similiarly upright or inverted once started and properly tuned.

Typically when someone states that "running it upright or on it's side" cures the problem, it is because they have cleaned up some other issue in the process.

That said, for me the Evolution 1.00's have been a horror story no matter their positions...

Yet I run the marjority of my glow engines inverted w/o problems.