"I'm still wondering why not set it up
as outlined on the Vanagon.com website:
http://vanagon.com/info/faq/#electrical.  No wires running under the
body to the starter battery, new relays, etc.

It seems this is how VW intended it to be done."

NOT how VW Intended it to be done...
We had this debate last January... February...

The conclusion seems to be that NONE of the Westfalias ever came with
auxiliary batteries, and that their wiring was NEVER intended for the high
amps that a drained battery can draw through the wires. As posted
previously, I measured  a 40 amp or more  draw by my auxiliary battery under
draw down conditions... I don't think VW ever intended that to run that many
amps through the stock Westfalia wires which are 2.5mm or about a #13 wire!
It's obviously dangerous. And it's not fused!

Apparently only the Weekenders came with an auxiliary battery. The Weekender
was supplied with 6.0mm wire to the auxiliary battery (about #10). Even this
wire size (and the stock 30 amp relay) is marginal for the 40 plus amps
drawn by a discharged auxiliary battery.

If you want more on this topic you can refer to my March 10 post: "Auxiliary
Battery Madness (looong)" and several posts by Harald in the
January/February period.
In light of these discussions, I believe Coyote is negligent leaving
information that you refer to at http://vanagon.com/info/faq/#electrical
which claims, "Many Westy's came from the factory wired to accept an aux
battery." It just ain't true.
In fact, he may be ready to change it since he requested (and got) my
permission to publish my "Auxiliary Battery Madness (looong)" post at the
vanagon.com site.

Be safe,
Good Luck,
Bill
90 Westy Syncro