That’s a good question… The static load limit likely means that the unit is not accelerating (or moving with wind resistance). I would think that a worse case loading could be during a hard braking incident with a load having a center of mass well above the camper top — this would put a moment (torque) on the mounts/rack which may be problematic. For example, if you had a 150 pound load but it’s center of mass was high, this would cause a greater moment during breaking than a load of the same weight that has a lower center of mass… There probably isn’t an easy answer to this question, but it makes sense to keep in mind the difference between a static load and a dynamic one.