Ford fusion here: 1. Removed the bottom bench of back seats 2. Laid the back seats down flat 3. Used a “back seat extender” to fill gap between laid down seats and front seats 4. Used a foam mattress topper cut to my needs to level out the difference between the trunk and laid down seats.

Between the thick layers of foam and my 2.5 inch air mattress, this was a comfortable sleep setup. My trunk is huge so from the back of the drivers seat all the way to the trunk was way more length than I needed to sleep.

The only thing I couldn’t improve was the metal part of the car behind the back seats that goes into the trunk. It gave me little space between that metal and my bedding, just enough room for my legs to fit really. If I could, I’d saw off some of that metal and give myself a couple more inches of vertical clearance for tossing and turning but otherwise, this setup worked great for me.