I'm not qualified to answer the first two questions, but:

Geza Polony typed:

> 3) Has anyone done a mod that allows for convenient external charging of the
> aux battery?

On my electrical panel (see
http://picasaweb.google.com/j.michael.elliott/MrSquirrelSSolarRig02 ) I
mounted a pair of those inexpensive push-in type connectors that you
find on the back of speakers (Radio Shack, I think). One is wired to the
aux battery, one to the starter battery. When Mellow Yellow is not in
use for more than a week or so I connect a pair of chargers (Battery
Tender Plus, http://www.batterytender.com/default.php?cPath=11_2 - there
are other suitable chargers) to the connectors. They seem to do an okay
job of keeping the batteries happy. Each battery gets its own charger
because they are not identical battery types.

--
Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
KG6RCR