Is the roof rack loose because the rivnuts are loose in the body? The rivnuts can be tightened if you can get the screws out. If you can not get them out, you will have to cut the heads off of them unless they will pull out. The rivnuts are a GM bastard size. You can get rivnuts that are large enough to fit, with a slightly larger screw. The screws are stainless. Panhead screws will work, to allow the cross bar to move, if you need to redo the rivnuts. You will probably have to go to a 7mm, or the approximate size in inches for it to fit into the hole snugly.