a Van top from carbon fiber, while it would be very trick, from a practical
standpoint makes little sense.  Unless you're Bill Gates or Jay Leno or
someone with lots of money to spend on a questionable project.  The amount
of material you'd use to make the part...fiberglass or carbon fiber.. is a
lot.  Glass fabric is a little heavier and not quite so stiff, but it is
about 1/100th the cost of carbon fabric..In a piece as large as a Westie
style roof, you might save oh, say 20-30 lbs, by using carbon fiber rather
than the normal glass,  but you'd probably spend $500 doing it...You could
save almost that much weight just by vacuum-bagging a fiberglass lay up and
being very careful with the fabrication..
  Now, in a racecar or a bicycle or an America's cup yacht or an
airplane...that kinda dollar per lb. may be worth it..but for the top of a
Vanagon?  Prolly not to normal humans...
  Don Hanson