Usually the load limit for rooftop racks is set to minimize the risk of roll-overs due to the center of gravity being shifted too high, not the strength of the materials involved. The Yakima racks themselves weigh 20-30# by themselves; that plus the carrier plus two hang gliders is going to be about 200# or so.

My biggest issue is not the weight or the CG problem. It is when you are driving on bumpy trails at low speed or freeway at high speed you get a lot of horizontal stresses that have to be supported. I am concerned about the FEH plastic towers that may not be up to that shear force long term, mostly in the side-to-side mode.