Matthew - I don't follow your "internal load capacity" vs "trailed
capacity" comparison.  I checked Helmut Zeidler's hypertext link he
posted today and, best as I can figure, my '85GL is rated to handle a
tongue weight of 50kg and to tow 2000kg (w/brakes) or 600kg (w/o
brakes)!  And THIS on a 12% grade!!!  (according to the TN DOT, all
Interstates are built with a max of 6% grade)  His chart also notes
tongue loads of 75kg for Vanagons man. after June '85 and 100kg for
those man. after '88.  Have NO idea what changes were made in the rear
of those later Vanagons, though, to increase their capacity.

Also, since the proportioning valve's function is to keep the rear
brakes from locking up, the downward force on the rear of the van
induced by an un-braked trailer creates even LESS chance of the rear
brakes locking up!  With a properly adjusted braked trailer, I fail to
see any problem which could develop.

I mastered most of the physics involved in "one object pulling another
through a pivoting tether", shifting loads, sudden
acceleration/deceleration and "emergency braking" from my years of
pulling calves from *issed-off cows!  It's just as breathtaking, I
think, as emergency stop in a Vanagon whilst trailing a load.

BOB - WA4RRN
'85GL - "Bourgeois"
http://dogmandoesAtlanta.com