I'll be reading responses to your questions with great interest, as we are contemplating moving from a TT to a Fifth Wheel, and also have a short bed.
I've been researching this and the arrangement I am contemplating installing is a Trailer Saver BD3 Air Hitch, and a plain Sidewinder (no air), as opposed to the 5th Airborne Sidewinder. The difference in cost between the Sidewinder and the Airborne Sidewinder is so great that I can buy a new Sidewinder plus plan to pick up a slightly used BD3 hitch and will come out spending less. Plus I feel that the BD3 will give me more air cushioning than the 5th Airborne Sidewinder.
Good luck, and please let us know what you decide on and how it works for you.