When I had this problem, my search led me to this site https://github.com/epkboan/myhome/tree/master/garage_door. There is a detailed manual that is compatible with all models. I had one of these a long time ago. I don't remember exactly which model, because I had to move immediately after I had...
Everything will depend on what goal you have. If you want to spend the night in the backseat, this is a good option with perfect dimensions. If you have a long journey, it will become a problem for your back, then you can also look at regular mattresses...