Hello, The rubber cargo floor mat from the dealer is worth every penny. It is a perfect pre cut to your floor with the cargo hold down rings cut out as well. Durable enough for your heavy gear. I abuse my floor with scrap metal and glass and the mat is holding up great.
I bought the plain steel floor then bought a piece of indoor/outdoor carpet from Home Depot (about $50), cut it to the right shape, and bolted it down using the tie-down hooks.
I built a shelf for the front of the cargo area using a 3 ft x 6 ft piece of plywood and some 2x4 bits, and a piece of steel angle bolted to the existing holes in the side rail to support that end of it - this is going to be a combination sleeping platform and additional off-the-floor storage. This way I can leave my foam mattress and sleeping bag and pillow in place. I cut a corner off the plywood so that I can still get in and out through the side door even with the shelf in place.