Extended bed camping platform?

Anyone make an extended bed platform for camping in their truck?

I have a six foot bed, I'm six foot two inches tall. I camp with my with lovely wife and idiot dogs. All four of us camp under the truck cap of our Tacoma, but its a little tight. We also do quite a bit of 4x4ing to get to our preferred camping spots, so large and elaborate setups that rely on ground anchors are not an option for us. Ive been thinking about building a platform using a bed extender like this:

I envision dropping the extension down and simply sliding a plywood/2x4 platform out to bridge the gap between the either the rear tailgate and the extender or the rear bumper and the extender. It would turn my 6ft bed into a 10ft bed! Next thing on the list would be to figure out some tarp/cover for it.

Anyone try something like this? Hopefully its comfortable enough for the dogs to sleep on the platform. I would love to wake up to the sight of my wife instead of my dog's ass.