Truck bed & slide in question?

I recently purchases a 2013 Chevy dually pickup & it came with a 5th wheel hitch installed. I pulled all of the pins & removed the upper portion of the hitch & now the only remaining part in the truck bed are the 2 rails that are bolted thru the bed into the frame. I can now haul full sheets of plywood. My question is; do I need to remove the rest of the assembly, before I can put a slide in camper in it? I can put several 2x4's width ways & they will sit just a bit higher than the hitch rails and this will make an even surface for the TC to rest on. If anyone has any experience with a set-up like this, please share your knowledge with me.

Thank You, Bruce