Here is the "slip" version of the pump in tank system.
The exact location of the cross over vents is open for argument.

BTW in my Cessna the two tank vents are connected together with only
one opening pointing forward under the wing to receive dynamic pressure. 
I assume Cessna thought that this would equalize the pressure in each tank and 
equalize the flow when on "both". It does not appear to work
however :-) I know not why. Perhaps a bug found his way into only
one of the vents tubes.
 
Paul Lamar
 
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