Here are pictures of my simple camper conversion. I needed a bed for two, a sofa, a table, a place for a cooler, it had to be easy to install and remove. I built this during a week and then we went on a 3 week camping trip spending every night in it. Overall, it works well for us. 3300 miles on the trip and averaged 29.0 mpg.
I have since removed the top half of the folding seat back, it is more comfortable w/o. The eye bolt thing on the rear door holds the door open a couple of inches for ventilation while at the same time being able to lock the door. The third cushion fits nicely behind the seat back. The unit is held in place with 2 turn buckles, 1 in rear shown in pics and the other is at the L mid tie down point. I can remove this in a few minutes by myself and have an empty van again.