I just got to try out my new sleeping setup last weekend with the wife. It worked wonderfully. I built a simple drawer/storage system out of plywood to serve as a base for a Millard Trifold Memory Foam Mattress. I would say the mattress sleeps as well as any budget memory foam mattress. I didn't have any issues with chemical smells or heat retention (although it was in the low 40's).
My storage platform is a two-piece setup where the front can be removed if I want to have the second row seats installed. The top of the platform is basically even with the top of the wheel wells. You would have very limited headroom if you used this mattress with the second row seats still installed. The mattress is a queen and is a tight fit, the front seats have to be slid forward for it to unfold. Comfort wise I don't think it can be beat. Pardon my gray door and missing panel, I'm converting the interior to all black and have procrastinated on the door upholstery.
My storage platform is a two-piece setup where the front can be removed if I want to have the second row seats installed. The top of the platform is basically even with the top of the wheel wells. You would have very limited headroom if you used this mattress with the second row seats still installed. The mattress is a queen and is a tight fit, the front seats have to be slid forward for it to unfold. Comfort wise I don't think it can be beat. Pardon my gray door and missing panel, I'm converting the interior to all black and have procrastinated on the door upholstery.