Regardless of the any rail system purchased by any MFG, maintenance will be required. Rail systems that penetrate the roof require maintenance as it relates to the re-caulking and the screws it is bolted down with. Rail system that attach to the seam of a roof, require maintenance as it relates to components used to pinch the part to the roof seam.
Clamp-on systems cannot and should not be attached to a 2" wide seam. The seam does not have the necessary strength to withstand the strain put on a snow retention system from the snow. Ultimately the system will fail and not only will you have to replace an expensive rail system, but there may be unrepairable damages made to the roof. You would possibly have to replace the roof and you would end with with a bolt down system anyway and the maintenance that goes with it.