I would simply not trust a suction pad for this purpose as long as I do not have the pressure surveyed like on vacuum lifting devices for cranes.
If the load on top of the car is heavy enough that it can kill a pedestrian, cyclist etc... in case of a failure, I simply don't want to bear such risk.
If the load on top of the car is heavy enough that it can kill a pedestrian, cyclist etc... in case of a failure, I simply don't want to bear such risk.