[skyking]

If you are towing your 5th wheel with the shortbed, you will need a slider hitch. I have used the demco manual hijacker with my truck, and it did not move far enough. I could still get cab contact with an 8" travel.
I got an Industry Standard Rail pullrite to install now, it has 14" of automatic travel and from what I can see it is the best thing going. You can get the OEM drop ins but I got my used at an extreme discount.
This all leads back to my comment about fairing the trailer to the truck. I have a design in mind that will either run a roller on edge of the trailer or track the side of the hitch to drive an opening of the side door. The door is closed with a bungee or similar.
Put sufficient clearance in it to allow for all high speed maneuvers, and only need to articulate during city street corners, parking lots, gas stations etc. It will be fun to design with the action of an autoslider to add into the mix
My original plan bumped up over the cab and faired the top onto the trailer, but that is not so necessary with the new aero noses on the 5th wheels.
If it was kept at cab level and just kept the pesky crossflow out of that gap, and sealed close to the bed edge I think it would be significant.
The cool part of that is it leads to a complete shell with a few added pieces that you stow behind the cab in that dead space between cab and hitch. Unhook and then piece together the shell for local adventuring.