The load warrior sits on the rails. It does connect to the crossbars, but all of the downward pressure is on the rails, not the crossbars. When I had my spare tire up there, I used the Yakima Spare Tire Mount which locked the tire to the rack.

If you go with the Yakima rack, get the locking clamps. For only a few dollars more, these will at least slow any thieves down from stealing your rack. An extra measure of security would be to put a cable lock through the rack and the rails.