Everyone at the dealership told me I wouldn't need a slider with my shortbed Ram, but since I have a steep driveway that I have to back down to park my Sundance in the backyard, I decided to play it safe and get the 16K slider. It's a good thing I did, when I tried to back the 5er down the hill beside the carport (have a walk out basement) to put in on the pad next to my garage, the rear corner of the bed just barely kissed the bottom of the camper, I pulled forward, slid it back, then backed down the hill with no trouble.
If you have a 4x4 TV, a slider will save you from the same situation since 4x4 TV's normally have a bit less clearance over the bedrails than a 4x2 TV would pulling the same trailer.