[QUOTE=CafeenMan;11667259... such as control line combat where the planes are flown violently. They tend to use bladder tanks. I'm not sure if this is the primary reason, but a bladder tank will always pick up fuel until the fuel is gone or the engine quits because there is no air ever in the bladder QUOTE]

I think the main reason the combat guys us a bladder is that the bladder is blown up like a balloon providing a heap of pressure and the fuel is squirted into the venturi under pressure and not relying on suction so much. The bladder tanks (like the Tettra ones) doesn't rely on the bladder to provide fuel pressure, it's just there to keep the fuel and air seperate in the tank. Muffler pressure can be still used with that type of bladder tank.

It's key to remember that different setups can be more critical to changes in fuel pressure. I ran a cheap engine for years on 22% castor oil with good success, then changed over to 20% synthetic and could never get it to run right for a whole flight. The drop in fuel viscosity from 22% castor to 20% synthetic was enough to make it too sensitive to changes in fuel pressure from full tank to empty and for nose up to nose level.

Tank height can be a source of a problem but it won't always be a source of a problem...