RE: 4 strokes
Your high tank position could cause flooding when the engine isn't running (use hemostats to pinch the fuel line until you're ready), but if it's not REAL high, most engines will tolerate it. Work thru the tuning dance, and if it can't be tuned successfully, then address the tank.
The flooding potential can be eliminated by using a uniflow tank setup, where both the supply and vent lines are set up with clunks. A separate "filling vent" is used to vent the tank when it's being filled, and is plugged when running.
J