Sorry, I got a bit mixed up and was skipping a step. An overlap can exist between boats on opposite tacks, however port is still the give way boat. Case 75 of the casebook shows an example of this. Starboard must still maintain a proper course though.
for example aas boats approach a bottom mark (rounding to Stb) then the boat on port has rights if he reaches the 2 boat area at the same time as a Stb boat. He is overlapped with him from the time he started sailing on port.
It matters who is inside or outside boat. Port isn't necesarrily overlapped with starboard when he gybes onto port, it depends if there is an overlap, would you call an overlap if you're at opposite corners of the course?
