Experienced sailors note that when you are sailing by the lee downwind with your sail on the starboard side, you are still on a port tack even if the wind is coming over the starboard side of the boat.
Experienced sailors note that it is the aftmost point of the boat that determines the overlap line. This will usually be the back of the rudder stock, though in some classes may be the rudder which is under the water. The front of the boat is determined by the hull and her equipment in the normal sailing position, so a retractable spinnaker pole counts if the spinnaker is up.