If something is specific to an individual program you may not find a reference for it in the GSP section of your PADI Instructor Manual. Head to the program related to it and you'll generally find additional equipment requirements in Section One - Course Standards.
Any time a cylinder is damaged or exposed to high temperatures it should be hydrostatically tested. This is to ensure that it is still structurally sound before being filled again as a damaged or weakened tank has the risk of rupturing.
making sure equipment fits is more than just making sure it's comfortable. We should consider some safety factors too.
The BCD must supply sufficient lift and neck seals should be effective restricting water but not blood flow.
The U.S Navy table is based on a different decompression model than the PADI RDP, therefore, you cannot transfer pressure groups between the two models.
The ambient pressure at altitude and if we assume that the percentage of oxygen in air is 21% that gives us a partial pressure at 1 ATM of 0.21.
If we multiply that by the ambient pressure at the altitude we will be diving (0.21 x 0.8) we will get the PPO2 at that altitude.