Ok, I made it out alive from the back seat. Here are some thoughts:
In order to get back there i had to sit in the front passenger's seat and scoot the seat forwards as far as possible. Couldn't adjust it while standing outside the car. I also had to loosen the seatbelt from the little strap that holds it to the side of the shotgun seat. Getting in was relatively easy, but when I leaned back I brushed my head on the part of the roof just in front of the rear window. After getting seated I found I had only a few inches headroom clearance. The seats were very snug, like something you'd expect in a race car. Leg room was not great, though and I wouldn't want to be back there more than about 15-20 minutes, tops! The tunnel in the middle takes up a lot of footroom.
For the record I am 5"11" and 160 lbs., size 11 shoes