Man that looks comfy! I gotta figure something out. Seeing that makes me want to turn the ply wood I have in my garage into a make shift (temporary) platform I can put in and out before trips (like Moab).Ohhhh... I was thinking you had drawers. Of course that makes sense now.
About getting 80... I goofed by 2 inches. This is a 78" mattress. But if you just move the front passenger seat forward a bit, you've got extra foot room. You don't fold the seats up against the front. You just fold them down. Even without drawers, if you have a few suitcases in back, you can do basically what I do with my drawers, and make them your continuous surface to the back of the front seats. I did that last summer on the way to Wisconsin, before my drawers went in.
This self-inflating mattress makes the gap a non-issue. As you can see from the photo, its full, 78 inch length still doesn't extend beyond the drawers, meaning there is another 4 inches or so back there. I have my Maxtrax in a bag between the drawers and seats. Otherwise, just cram something in there, or use a blowup mattress, and you won't even notice the gap.
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I've got a couple 3.5" REI Camp Beds I picked up at their last annual sale, love them! Got the XL for myself and the regs for the wife. Normally when I crash in the truck I put down a 2" memory foam that I cut up to fit the profile of the back, it's not nearly as comfortable but super easy to setup and take down comparatively.