Question
Blue and Yellow approach the windward mark overlapped on port tack with Yellow to leeward and on the layline at the zone. Rule 17.1 does not apply to Yellow. Before Yellow passes the mark she luffs Blue head to wind. Blue responds to the luff and keeps clear. There is a Y flag. What should the call be?

Answer
Blue is required by rule 11 and rule 18 to keep clear and give room - and she does so. Because Yellows luff is inconsistent with rounding or passing the mark, rule 16.1 requires her to give Blue room to keep clear. However, rule 17.1 does not apply, and nothing in the rules prevents Yellow from sailing above her proper course while the boats are passing the mark.
Display the green and white flag.