I have a newer Montana and a F350 short bed (6'8"). I went with the Reese manual slider and have never slid it. I have jacked the trailer backing up with a dip and never came closer than 3 inches from my cab.
Much depends on what length short bed you actually have and what configuration the front of your fiver is. For example if your bed is actually 6'6" or less and your fiver is pretty squared off in the front you will probably be using that slider a lot. Also don't forget you want a minimum of 6" or 7" clearance between your truck bed rails and the underneath cap of you fiver.