No big difference.

If your carb is adjusted properly and the fuel plumbing is non-restricting, you'll have no problems.

The fuel tank height issue is a bit of a myth that is often propegated here.

Turning the plane over will offset the tank height by all of .5 to 1"... not enough to even register for most planes.

Remember that if such a different was that important to our planes, we would never be able to perform uplines or downlines.

That said, proper tuning does involve adjusting the plane with the nose up and down, to verify that the engine will run correctly at all attitudes.

It is normal to see SOME change when the plane goes nose up or down, but you are also moving the fuel tank a good 4-8 inches or MORE up or down when you do that...

This is MUCH more of a difference than the plane experiences when inverted.