I'm going to go there. I'll probably regret it.
I have a back seat problem. It's my size. My first ex and I decided we were going to get it on in our Triumph when we were newlyweds after a couple of unsuccessful drunken efforts that ended up outside. We hung a towel over the garage window and got naked before we got in the car to minimize the difficulties. We worked pretty hard at it and could not get it done until I put the top down. I'll leave that to your imagination.
Now you know why I've always carried a sleeping bag in my car. It's not survival it's emergency services. I still prefer the car....