Eric Miller wrote:


I think the lower tank does empty itself... but just until it gets to the
level of the fuel vent.
In the BOTH setting, they'll both empty to the level of their respective
vents.

There is only one vent, under the left wing. If fuel expands it runs in
a line between the left and right tanks. This line is above the tanks.
Fuel will also go thru this line if the selector is on both, the tanks
are full or near full and the plane is not level. Move the selector to
either right or left and this won't happen. If left on both the tanks
will level themselves thru the selector.