I had popped the seats in the car just to facilitate shakedown, and to make the local constabulary less interested in the car as it went by. Bad enough that it was unusual and did not have matching wheels !! However, everytime you look at the car from the rear, the unfinished backs of the headrest were visible complete with dried glue stains. 
To an observant police officer, this would still say “Allo allo allo, what have we here ?”. With the need for testing which might on occasion exceed posted limits, this vehicle needed no more attention than it already received. The fix was simple, but involved pulling the seats out again. I finally got around to finding the cardboard backing, and grabbed the spray adhesive. A few clamps and some patience. Easy peasy, and problem solved. Now on to more important issues….