All of our parts are mounted on a rails system (OEM MB rails or our own rails system). By using a rails we divide the weight across the roof. This also creates the option to remove the rack without access from theinside of the van later on. It is possible to position the loop and parts across the rails. In case you have a rear camera, you might need your roof rack slightly more forward than a van who does not have the camera. Same goes for the roof windows which might be located somewhat divergent.