> Is there a weight limit that a pop up can handle while it is open.

Well I have had the top raised on my '81 Westy with three bicycles
attached to Thule rack attached to pop top.  When I attached the
artificial rain gutters I located them in the center of the van rather
than towards the rear.  This makes the top more difficult to raise, and
with the above load it is definitely a two person job.  If I had to do it
all over again I would locate the rack towards the rear of the van, and
still may attach another set of the artificial rain gutters back there.

The above mentioned racks and bikes probably weigh on the order of
100-120 pounds, and this is about the limit of my comfort in hauling
stuff up there.  I have had no problems with this setup.

>Also, what weight can the upper bed hold in one of these things?

I'll second the 400lb weight test.  My wife and I have slept up there
many times, no sweat.  Now getting out of there in the middle of the
night to take a pee break and climbing back in without elbowing or
kneeing your bedmate is a challenge..............

Tony

Anthony L. Mourkas
Hampden, Maine, USA
1981 Vanagon Westfalia