Well well well, we all like this subject, now don't we!
For what it's worth, Thom should keep his bus 6 volt.

Yes voltage doublers are ineffecient, but so is everything else.  Like power 
generating stations, etc.  What's more, the kind that I know of will not work!  
This kind of circuit is not made to supply any sort of current.  I think 
that we were talking aroung 5 amps, right?  When any sorta current is drawn 
from them, the output voltage drops real fast, so you're right back where 
you started from.

I think that 2 6volts are much easier.  The person who posted that you 
couldn't use the fridge when you're charging the batteries is right.  Well, 
you could charge one at a time and still use the fridge, I think.

Think about it, I'll produce the circuit if needed.
  Chris Bridge
  
  Currently building an engine for a ''71 Westy
  E-mail cbridge@vt.edu