So,

I was getting about 13.5-13.8 volts at the alternator, but only around 12.5
at the battery.  No change with RPM.  So, to the archives, lots of reading,
studied the Bentley, some threads on thesamba.  This has been going on for
some time, battery was running down, seemed to be getting worse.

Turns out it was a loose nut on the alternator, the D+ connector I think it
is called, where the 2 red wires connect on the top.  Of course being
somebody who knows it all, at first I concluded a new regulator or
alternator is in order.  But.....after some reading, and all the advice, I
changed and figured that bad grounds, bad connections, or possibly damaged
wires were the most likely cause.  Very odd, the nut holding those ring
terminals on the terminal was loose, I could wiggle those connectors back
and forth a bit.  The nut itself is somewhat binding on the post, so not
sure how it got loose.  Maybe a left over from when I fixed the alternator
bracket over a year ago.  There was no lock washer, except on the other nut
that seems to hold this post or something.  So cleaned (filed, sanded) all
the parts and tightened.  Nice voltage at the battery.   Thanks guys, gotta
love those $0 repairs.

Roland
'89 Syncro

PS: found this article on gerry from 1995, very informative.
 ALTERNATOR CHARGING SYSTEMS
  How to avoid electrical generating problems - Motorhome, July 1995
  by Joel R. Donaldson
http://gerry.vanagon.com/files/motorhome/Motorhome-Alternator-Charging-Systems.txt