Looking at all the options I decided to build my own rear storage drawers. In retrospect if there was a decent available option for less than $1500 I would probably take it.
The amount of time effort, and problem solving that went into making a version 1 of this WK drawer is a lot, plus the costs start adding up quick. I used 1/2″ marine grade plywood, which had to be special ordered where I live. In the end I am happy to have it and feel there will be less chance of swelling. Given the quality of coating (paint) I used I probably could have gotten away with regular plywood, but who knows. Having a drawer that swells and binds kind of renders the whole operation useless.
The 500 lb lock in lock out drawer slides themselves cost more than $200 USD a pair. Incidentally I have an extra pair, as I decided it was ridiculous to go for two side by side drawers with slides and construction that heavy. The drawers are never going to hold more than a 150 pounds, so why lose space and add weight and expense by adding a second drawer?
This is all my logic and the process I went through, and by no means is right for anybody else. My build is for long term expedition travel. A big part of my process was figuring out how I would use it. Also I built the drawer to be able to house a Webasto CR 36 refrigerator as half the drawer if the future decides that is what we need. In this case the drawer will be halved.
This is my WIP final product.

The single large space is adaptable, and in it you can see one wooden box, of which the drawer holds 4, and still has space left over. These can be used to break up space as needed. The current cargo load in this photo is just what I stuffed in after working on it before going on a solo camping trip. Instead of bringing tools into garage, I just left them in drawer in case I decided to do more work over the weekend.

I began by mocking up rough space with chipboard. Most of the cuts I have done are with a table saw, or circular saw.
Deciding how to utilize the stock storage space (Ridiculous small space plastic Jello compartment) had me going back and forth many times to decide whether to leave it or take it out. In the end I took it out, and made a semi hidden storage space with this area.
Above: Initial build started pretty simple. I began using Dado slots for extra strength, but did not continue the practice for all joints.
Above: Initially I was going with the two drawer option, and made a double glued wood divider on which to mount center hinges. I still have this divider, and if I opt for the Webasto CR 36, I will use it.
Above: Engineered I-beam slotted into receiver for layout on drawer bottom.
Above: Here you can see the engineered I-beam and locking slots fit into stock receiver tab. This is not the strongest setup, but unless the Jeep is inverted, it should hold over bumps and bounces. It is all heavily glued and screwed.

Above: As you can see I struggled with how to mount electronics, relays, switches, battery etc. This was one idea, but it involved overly complicated slides and extra wood and not using the stock Tupperware. This option did not a lot of positive support.
Above: Little things like correct overhang, width of top spacers, load spreaders went through several stages, and in the end it was not perfect. Sometimes a design idea was implemented only to be cut off in a fashion that was less than perfect. More time in design phase would of course be a good idea, but in the end I needed to figure it out as I went along.
Above: Here is the primed semi-complete drawer Left side is left side, and the part down to the floor is what pushes against the rear seat. Since we are travelling with kids, the rear seats or some version of will stay. At the bottom you can see the locking tabs that fit into the stock Jeep receiver tabs for the plastic Jello compartment.
Above: Drawer assembly and final gluing. I used an overlap technique that allows for slightly less lost space from hinge width. Maybe a little heavier, but stronger and more work. Not sure it is better.
Above: Drawer gluing and spot putty of screw holes.
Above: Here you can see a test fitting. The white panel on the top is a door opening up against the cargo barrier. It is measured and designed so it will flip up and lean back against the barrier and stay, and has enough space to be able to do so, while still be able to access cargo through the top when necessary.



Above: you can see the raw storage space available as well as steel for mounting hiding, etc.

Above: Numerous fitments and tests were necessary throughout the build. Here you can see drawer slide bolted in to primer only version.

Above: Zinsser BIN sticks to glass without sanding, and seals in resin stains. This stuff has serious priming ability, and don’t expect to get it off of anything you spill it on. I had some left over from house repair.

Above: Paint and primer used were high quality, and specialized for sealing. The top coat is an Industrial genuine oil Alkyd Enamel. Most Alkyd Enamel are water based these days, specifically anything you can get at a big box store. This is basically a rust paint, but with more pigment and binder, essentially making a better overall paint. Don’t be surprised when you start seeing color accents on my Jeep that match my rear storage drawer. Have already started painting steel wheels. This paint takes close to 30 days to fully cure, although it is tack free in 7-24 hours depending on temperature and humidity. I just keeps getting harder.