With truck caps:
http://leer.com/Truck-Caps#.
Check out the 100RCC and the 180CC.

No cap? Then check out: http://www.tracrac.com/, and if you want to be able to put in a cover over
your truck bed you'll need this one:
http://www.tracrac.com/pick-up-trucks/tracrac-g2 otherwise it is much less
expensive to go with this:
http://www.tracrac.com/pick-up-trucks/tracone. Both are removable, the first
one comes off easier.

You might also look at this one:
http://www.bikerackshops.com/TU422XTPS.html, although why you would want
your rack to be adjustable for hang gliding is unclear to me. The Tracrac and
the Thule rack make it easy to load your hang gliders  as there is no bar
in the way.

Check out the load carrying capacities of all the racks.