Well, good points by everyone. I fly helicopters, and not upside down a point that can make a huge difference. I have only used a 2 oz header tank, set so that the pickup is on the bottom, the fuel comes in at the top, my pickup in the main tank is felt covered. Never had a flame out, nor bubbles in the header after flight. Helicopters naturally make the fuel foam once air is in the top of the tanks.

For what that is worth.
Jack