Wouldnt a thick air mattress pumped up while it was inside accomplish the same thing?
a coleman queen is 78"L x 60"W x 18"H.
i camp and i wonder how the platforms work
^This. I also frequently use a simple inflatable mattress as it conforms to the interior quite well as long as it isn't 100% inflated. I have even used thick memory foam on the bottom and actually preferred that to the mattress given the lower height and increased headroom. I hated having my head up near the roof.
As other's have said, at the very least, I would add a wider footprint to those 2x4s so you don't cause any damage.
What you guys are failing to appreciate is all of the room UNDER the platform for storing all of your gear. Just inflating a mattress would require you to unload and reload all of your crap every night, perhaps leaving it in less than perfect weather.
I really dig the storage space underneath i would get some different supports though like stated above, ive always thought about doing this but then i made a pallet in the back of the 4runner on an offroad trip and it got under 20 degrees and needless to say it turns into a metal freezer:smow: . Ive been a tent guy ever since.
Looks good, but I have a couple of recommendations/suggestions:
First, IMO that's too high. You're going to have a hell of a time getting in and out of that and you won't be able to sit up at all. It's going to be like sleeping under a bed.
The reason your platform is so high is to clear the bottom cushions of the back seats when folded, yes? OK, you can take those cushions out in literally about 4 minutes with a ratchet and a 14mm socket. Seriously, 4 bolts, 4 minutes max. That will let you drop the platform a few inches and not lose any length.
Second, you really should consider some kind of cross-bracing for the "legs." There are several different ways you can do that, just use your imagination.
3/4" plywood is going to be VERY heavy! I used 9/16ths (1/2) on mine and it seems to work fine. Is there anything holding it down to keep it from bouncing around? I guess if you don't go off-road this isn't an issue.
You can invest in some of those long plastic tubs to slide underneath the platform for "drawers." Makes it easier to get your stuff out.
You can check out my build if you want some ideas, I also built a platform last year and it works pretty well. The link is in my signature and the platform build starts about halfway down page 3.
It almost negates the need for a platform if you don't need to carry a lot of stuff and don't need lots of room for sleeping. If it's just me I only need to take out one seat bottom. I think I'll see if I can get by without a platform now!