At Wednesday's rules seminar at CGSC, Nick Voss and Augie posed a question I couldn't answer about the application of the new Rule 18 between two boats at a leeward mark. I've added some detail to describe a very possible scenario.
Yellow and blue are approaching a leeward mark to be rounded to port on opposite tacks, in 5 knots of breeze, slight chop.
Step 1 (below). Yellow reaches the Zone with Blue overlapped inside her.
Step 2 (below). Yellow douses her spinnaker and bears away to a run, slowing from the takedown and deep angle. Blue, wishing to maintain speed because she's still 2 to 3 lengths away, leaves her spinnaker up and continues on her angle, possibly with a slight luff to take Yellow's transom. With greater speed she crosses astern of Yellow and estalishes an overlap outside Yellow.
Step 3 (below). Yellow is now between Blue and the mark. Yellow is somewhat slower, and Blue has to avoid her and round outside and protests, claiming Yellow, by her presence, did not give her room to sail to the mark, or room to sail her proper course at the mark.
Who broke what rule, if any? How could she have avoided doing so?