I saw on another thread a person could add an interior pocket to a pack bag with a slick clip. How many attachement points are in the pack bag (3900) and where are they located? Any pictures you could post showing this?
They anchor at the frame attachment. You can place internal or external of the pack bag. There will be a larger size like a hydration pocket that is also useful for basic organization or a bladder on the outside. There will also be a small sort of wallet sized pocket great for valuables.