1967brutus

Without reading the full story, I can say this from experiments I have done:

At full throttle, muffler pressure is in the order of mangitude of about 20"of fuel column (very easy to test by simply using a 3-line set-up and attaching 3 or 4 ft of fuel tubing to the filling connection, leading it straight up and see how high the fuel will be pushed up at full throttle). Not saying it IS 20", I have seen 25, I have seen 15, but in general, "roughly 20"
A typical glow engine also has a suction head of at least that amount or more, which can simply be tested by placing an engine on a bench, using 3 ft of fuel tubing and a loose fuel tank. No muffler pressure. Run the engine at WOT, gradually lower the tank while simultaneously readjusting (opening) the HS needle. At some point the engine will not draw fuel anymore regardless of how far you open the needle. This height that the engine manages to pull up fuel is the suction head.

All in all, that means that there is roughly about 40" of fuel pressure difference present at the NVA.

So yeah, that 1 or 2 inches of fuel level change in the tank from full to empty really is not going to do very much, and even holding the plane vertical (maybe 4" of height difference between fuel level and spraybar?) is not going to really affect things much. A bit, because the leaning out in this position IS noticable after all (engine will gain a few hundreds of RPM).

Things change though, when doing sharp manouvres. Sportier RC planes have no issues pulling 10G or more. and suddenly a 2" height difference becomes the equivalent of 20"...
Nothing to worry about for a sedate floater, but for an F3A plane proper tank location DOES make a difference.