If the rear headrests are in the way, just fold the entire seatback forward. Before I pulled my rear seat out completely, I used to leave the seatbacks down all the time. They flip back up with no trouble at all.

Regarding hanky-panky, if you remove the headrests from the front seats, the backs will go back down to horizontal and just meet the front of the rear seat, and then the rear seat backs will also go back down to horizontal, making the interior of the car one big, if slightly lumpy, bed.