I dislike having to make this sleeping platform for the back of Frida, my MY2010 Land Rover Freelander2, however the seats don't fold flat and the 2.5 degree slope means you tend to slide downhill if you just use a sleeping mat or two. I've only got 1.5m (60") of length and I'm 1.86m (73"). To give me a stretch out alternative I have the panel on the side which gives me 1.8m diagonal and I can close the tail gate. I have rain deflectors on the side windows so I can have them down an inch for ventilation and I have ordered some mesh sleeves so I can have the windows down all the way on hot nights and keep the mozzies at bay.
The build was simple. I measured and worked out the pieces I would need so I can store/transport it with the seat in use. The side panel doesn't fit snugly underneath, mores the pity, but I'll work something out. The hinges on top make for easiest deployment and stowage as the 17mm melamine boards are quite heavy.. With a couple of sleeping pads on top I don't feel the hinges and I might tape them so they don't wear at the pads. I could get some 100mm foam cut to size but that is more expense and they are bulky. Melamine was $42 and I had it cut to size at 7 cuts for $0.50 each plus a free first cut. Trimming the end to fit with the seat up was a faff with a fret saw, carpenters saw, electric chainsaw and a grinder all put to good use.... I couldn't be asked getting the jigsaw out and an extension cable: note to self, buy a battery powered jigsaw. Hinges and screws ran another $25.
The end result is basic, utilitarian and it works. Now to nip out and test it on a quick solo overnighter!