you might look into the Sea sucker bike mounts.
http://www.seasucker.com/product-category/bike-racks/ They use vacuum suction cups that go direct to the top of the van and are easy to transport from vehicle to vehicle. There is a great thread with pictures on the mtn bike forum
http://forums.mtbr.com/car-biker/seasucker-587996.html I now travel with one on our trips as it fits in the suitcase easily and we can use it on rental cars. I used it last month for our Calfee and it worked great.