Great idea Mark!!
I do almost the same thing to travel with my dogs. I have a deck in the back with spares, etc under it. I remove the passenger seat back and place a plywood deck on the passenger side, from dash to back door.
But, my back requires 5" of foam and a ThermaRest Basecamp pad... So, I lay the sleeping bag out and cover it to allow my dogs to travel in comfort. We overnight in 44 and pitch a tent for multiple nights. Good sleeping for two Golden Retrievers and one old man!!