Posted for Charlie Kohler <charliekohler@yahoo.com>:

 
 Hey Colyn,
 
 Years ago I worked in an engineering department and was given an assignment
to make a water pump that would not cavitate. I found that once a cavitation
bubble began, it was extremely hard to break if not impossible.
 
 Point is, if you add fittings/90° bends/ "t"s in the main fuel line, you
increase the likelihood of a cavitation developing which you will not be able
to break and get the engine running again.
 
 An easy solution for the auxiliary tank is to plumb it into a vapor return
line with a "T" behind the main spar.
 
 The technique would be to burn down the main tank (let's say the left) with
the aux tank connection--switch to the full tank (right) --open the valve to
allow aux tank fuel to go in to the left tank through the vapor return line.
Fill that tank back up--turn off the aux tank--return to using the left tank.
In this way you never have the aux tank connected to the main fuel system
plumbing. No chance of vapor locks. No chance of cavitation.
 
 Just be careful to not open the aux fuel tank valve when that tank is
selected for use. The fuel pressure would upset the aneroid in the engine
driven fuel pump. (Or worse)
 
 Charlie K.