>On the subject of backup fuel switching: If you have a ganged mechanical valve, why bother with the electric one? :-)

Two expensive three-way switches vs a single on-off valve.  After sending that last email, I realized it was pointless to make a crossover for return side.  Here is my analysis:

You're flying along and at some point the electronic fuel goes tits up.  It is now stuck on one tank.  You won't know until you go to switch.  You can:

A) Do nothing.  The fuel will continue to pull from the one tank.  This would be the sensible option if you're close to landing, or if the tank has plenty of fuel.

B) Open the crossover valve.  This effectively tees the fuel supply lines.  This would make sense if the active tank was extremely low.  The high, inactive tank should now flow fuel into the low one.  The return line will still be routed to the low tank, also filling it back up somewhat.  It will not be possible to overfill the active tank unless you opened  the crossover prematurely.  IE, open the crossover valve to pull fuel from both tanks and return fuel to the active one.  You could even close the crossover once the active is half full.

The part seems to be readily available from auto parts stores, so a precautionary landing and replacement should be simple.