Mike - if they are still subject to 18.2(c) then A gets to determine proper course. If B breaks the overlap, then re-establishes it, yes, they are subject to 17, but then they get to sail their proper course.

May not make much of a difference in one-design, but it sure makes a difference in dissimilar boats, especially if one (A) carries a symmetrical chute and another (B) carries an asymmetric.