RE: I need an airplane rack system for my van
You can also put a machine screw in the ends of PVC so you can screw it agains the window. Put rubber on the head, like a cap, and let it sit on the window sil and back the screw out to hold it. Works well too. The PVC racks work really well. In my truck, I use 2X2s across the rails on the topper held on with C clamps, but that wouldn't work so well in your van. There are lots of good ideas. Good luck