>So, what is really needed is  a way to insulate the van properly (as was
>discussed this summer) and improving on the existing system to increase
>air flow. Ideally VW should have had a third tube running up to the rear
>seat and a way of recirculating all the hot air inside, plus a lot of top
>quality insulation in the doors, roof and panels.

I saw some after market setup where one cuts a couple of holes in the back
of the bus, and installs a fan back there.
The fan draws cold air from inside of the bus and pumps it through the heat
exchangers.  Another fan up front sucks the heated air into the cab.  The
whole thing is supposed to act by air-recirculation, and the inside of the
bus will gradually get warmer.  Rather that continually blowing fresh, cold
air through the heat exchangers, you use air that has already been heated. 
Plus, heated air is circulating through the van.

Your heat exchangers better be intact, otherwise carbon monoxide levels
could rise to toxic levels.  Maybe a carbon dioxide sensor hooked to a
warning beeper would work?

Wolfram