I found that strategically placed padding over the handbrake lever and in the gap (over the rear footwell) between the supine seatbacks was necessary, along with some Tylenol with codine.
It is not like falling asleep on the couch while watching TV.
It is like sleeping in a tent pitched on exposed tree roots.
But I'm not picky; there's enough in the backpack to stuff into the crannies and you learn how, about the third night.
Like many camping trips, looking back on it you had a great time!
Fred Widmer