We've now two dogs, both cocker spaniels, who travel quite happily on the back passenger floor. We lift the wider seat behind the passenger side front seat and they both snuggle down on the floor there, taking it in turns to jump up on the smaller seat on the drivers side to admire the view. They've both got harnesses attached to the rear seatbelt latches which allow them a degree of freedom in the back but stop them from climbing over into the front.
We use a dog blanket on the floor and another over the smaller seat but haven't needed to protect the doors as they don't scratch them being quite happy to just look out of the windows.
The smears on the inside of the windows aren't really smears, we call them cocker nose art.
We've had the Honda wind deflectors fitted to the outside of the windows and these allow the windows to be left down by about 2 inches without it being too noticeable from outside the car but anyone approaching too close is greeted by the Black Ninja Cocker Spaniel Tag Team.
We've the black Jazz Hybrid and the wife's choice of colour was because it matched the dog.
.....She's happy so I'm delighted.