FWIW, I have installed a rack system on two Westys so far and had no
problems. Using the existing holes in the Westy top, I would make rain
gutter brackets, drilling holes to match, using 1" angle iron and 1/4" round
stock welded on one leg, near the edge of the angle iron. A backing plate
behind the fiberglass provides reinforcement. This is the system I use.

Next, I took an old roof rack system for skis or surf boards, eliminated the
old straps and fabbed kayak cradles out of 10" PVC (using my micro wave oven
to shape them) and U-bolted them to the bars. I use a pair of those crank
tie-downs and a rope on the front to secure the load and the pop top at the
same time...nothing tests your load (or your nerves) like the 18 wheelers on
Mex One: yikes!

The Westy roof is indeed strong. The book says 200 pounds...my 'yaks are 50#
each plus I use them for cargo holds and I have crawled up there many times
with my 210# carcass to rummage for something.

Kit Carter, 85 Westy
central coast, CA