[John B R1T]

The 5 gallon "Commander Boxes" sold at the Orange or Blue big box stores fit nicely nested on top of each other in the gear tunnel. I use two, but six would fit.
Very handy for things like tie down ratchet straps, the ball and hitch insert for the receiver hitch, an old bedsheet in case you're wearing decent clothes when you decide to crawl under the back bumper to take off the panel and insert the hitch...etc etc.