Another Idea, other than the simply elegant lancair solution for header
tank, main tanks with two pumps.

In place of the facet pump on each tank, install a one way valve. On/Off.
Run both valves into a TEE which inputs into Facet Pump A.  Facet Pump B is
in line.  Each pump has a separate power circuit.  You do not want to have
the pumps in parallel with each other on the same circuit. If either pump
shorted out, the power would be unavailable to the good pump hence no fuel
to header tank.

Make sure that the Tee is at the low point of the fuselage before rising to
any pump.  Thus you can open both valves and tanks can balance out fuel or
you can operate from right left or both tanks to fill the header.

Rob is right.  I have yet to unport a main tank after 230 hours.

Complexity???  Two valves but more flexibility.

Bob Smiley
N94RJ