This is perplexing. NL says to just use a 4x8 sheet of 1" plywood and a 3/8 DeeZee mat for my camper and a 2016 Ram for proper clearance. The 3/4" stall mat does clear, so I'd think 3/4"+ plywood and a mat would work. However, 4x8 doesn't allow for full support. So now I'm not sure the best configuration of plywood to support the thing.
I have been sketching some cuts and even cut out some trials out of paper, but it seems a little complicated to me. The best options I've come up with leave a gap under part of the camper.
1) 1 sheet 4x8 plywood as NL suggests. (Doesn't support wings aft of wheel wells)
2) 1 4x8 sheet split into 2x8. Notch wheel wells and leave a gap down the centerline. Optionally add strip to fill gap.
3) 2 sheets of plywood both rotated 90 degrees and cut to width of bed notching around wheel wells. A small gap could be left to allow some overhang at back of bed. Optionally use some scrap to fill gap between sheets.