The trick is getting AP to admit the packaging is adequate.

However if the protectors were bent, it is unlikely that the damage was caused by heavier packages being dropped on them (or being dropped on them in a situation where ANYTHING could get damaged), which seems to be AP's only criterion. Bending would presumably be caused by negligence on the part of an employee/contractor and SHOULD result in AP accepting liability.

I would go with catspjs' solution, with the proviso that if AP don't admit liability there is an ombudsman you should probably take the matter to.