Figured this thread should get bumped since there seems to be alot of threads being created asking similar questions or looking for ideas.
I finally finished up my sleep platform and drawer system. Its a two piece system, so for everyday driving the drawers live in the back and dont interfere with the rear seats. The top is at the same height as the wheel wells and follow the contour of the panels.
When its time for a trip I install the sleep platform. Im 6'3" so I wanted as much leg room as possible...which means the seat bottoms need to be removed. Not a big deal, 4 bolts and they pop right out. This gives me a 6' platform that goes all the way to the back of the front seats (in their driving position), and with the passenger seat tilted and slid forward, I have 6'10" of leg room.
As far as construction goes, I wanted to keep things light, so the drawer frame was made from 1x2's and 1/2" plywood on top. The drawer were also made by 1x2's and have 1/8" plywood sides. The drawers are 35" deep and I used 100lb 28" drawer slides from Amazon. I could only find 500lb full length drawer slides and the price was way too much compared to the 100lbs. The latches are made by Southco.
The sleep platform is also 1/2" plywood with some 1x3's along the bottom to help support it. One end rests on a lip on the drawer frame and held with two 1/4"-20 counter sunk screws, the other end is supported by 1/2" x 18" steel pipe with threaded floor mounts.
The entire system can be installed or removed in a couple minutes. The only modification is removing the seat bottoms....which to me, is worth it for a good nights sleep so I can stretch out.
I still have some tweaking to do on the inside of the drawers and how I want to mount my camp stove and some general organization dividers, but all in all, Im psyched on how it turned out.