To the OP's questions, multiple drawers will allow vertical support in the middle of your platform, something that's useful if other stuff will be stored on top of it, or if you are using it as a sleep platform.
Multiple drawers also let you get to things when you have limited room to pull out the drawers, letting you stand to the side instead of beyond the front of the drawer. Multiple drawers will also cut the weight of the drawer contents by half or two-thirds, making operation of the drawers much easier and the needed weight capacity of any sliders much less, making those less expensive.
Multiple drawers is also a way to not 'show all your cards' to prying eyes. Put your most-used stuff in the front of one drawer. 1ts aid, recovery, roadside emergency stuff. Camping and prep stuff, calories and fluids, arms, whatever in the back or other drawer.
Finalizing designs now for my '02. it's 49" wide between the side fairings / wheel wells, just like a pickup bed. About 58" from the rear hatch to the back of the 2nd row seats. 30" from hatch to the back of the 3rd row.
I'm building a narrow module to the driver side of the cargo area fitting behind the 3rd row to hold additional batteries and power conversion and running many power ports / voltage flavors to both the rear and front faces. The remaining 40" of width will be split into two drawer modules, each in their own housings, extending all the way to the 2nd seat. Right drawer set up for desert rifle range trips, to hold / secure rifles and related gear. Left drawer will hold all the roadside emergency, recovery, tool, 1st aid stuff, most in task-grouped bags.
All components will be about 9" tall and form a flat carpeted floor altogether. I need the headroom for big dogs and rare use as a solo sleep platform.
The drawers will be fastened but readily removable, whenever I need to put the 3rd row seat back in. I can just throw a few useful bags of stuff in back, for whatever trip has me hauling 5-6 people. And that way the power module remains in place for camping, field astronomy, ham radio field day uses. I'm also working up a plan for a sturdy cargo net, which will have mounting points behind both the 3rd row and 2nd row seating, so the loose bags of gear (or other stuff) won't be a problem.
The 'tool' drawer will also have a 'tabletop' flat cover which is hinged in half to also be folded upward like an A-frame easel, for use as a mapboard / whatever. When stored it will either rest on the sides of the drawer, or slide into a set of grooves attached to the underside of the upper deck, like a built-in cutting board sort of thing. On second thought it will rest on the back two-thirds of the tool drawer, since it will be sized to fit into notches on the top edges of the drawer sides.
I'm not using any slides, using melamine coated board for the bearing surfaces, possibly some form of dry lubricant if needed, but likely won't be, and I'm designing the back end of the drawers to fit close to the ceiling such that they support the drawers when they are extended. Don't want the loss of space or expense of heavy duty metal slides.
I got some nice inexpensive large locking paddle latches from Northern Tool a few weeks ago, have since modified them for mounting with bolts, and given them a nice paint job. I posted a topic about those -
http://www.expeditionportal.com/forum/threads/135743-Best-value-place-to-get-paddle-latches
I'll get a design / build thread started soon with a bunch of illustrations, in the next week or two. I hope to have it all built by Memorial weekend at the latest.
And I'm interested to see how a finish carpenter chooses to do his joinery in such an application. At best I considered some rabbeting and glue and screw, trying to make strong joints in minimal space. I keep looking longingly at Kreg jigs but can't get past their required proprietary screws (I'm too cheap).
