That would then be a Rule 14 violation.

I am pleased to see seven references so far in this conversation to "sportsmanship", a basic principle of our sport.

When thinking of sportsmanship I always think of golf. If someone kicks a ball out of the rough back on to the fairway, or whatever, then they are clearly breaking a rule and simply cheating. And no one likes a cheat!

Sure it's a bit different in that competitor vs. competitor situations are rare in golf whilst common in sailing. Also the RRS are a bit more complicated and nuanced particularly when it comes to overlaps, the zone, proper course, and much more, so the breaking of a rule is not always as clear-cut in the sailing world.

I think it is critical that fair sailing, sportsmanship and safety be a constant focus when anyone joins the sport either as a child or an adult. I think one of the biggest issues is with adults who buy a boat and go racing in their new weapon with virtually no knowledge of or care for the rules. From a safety perspective, Organising Authorities that there is sufficient (current) experience on board to ensure the safety of the fleet as a whole.

There is also another cohort that is a concern. That is the children of "Opti-mums(dads)" where they encourage their child(ren) to win at all costs ... sometimes encouraging them to break the rules when they can get away with it and othertimes coaching them to weaponise the rules against other competitors :-(

I’ve heard of that race! Full disclosure, I’m Commodore of the partner club with CYCA, the RYCT. I have long marvelled at the weird start sequence used by the RSHYR. Hardly a typical event and I agree why it’s used in that instance and for the reasons you state. But am I right that you don’t advise a boat that it’s over until some minutes up the course? 

Thomas ..
  Both Case 77 and Case 91 when taken together imply your answer I think.   Both pertain to the obligations of a keep clear boat when  the equipment of the ROW boat is out of its normal position. 

A boom swinging from the starboard to port side is a boom operating in its normal operating positions.   A KC boat sailing DDW so close along side a ROW boat that if the ROW boat flops her boom over, without ROW changing course, that the boom hits part of the KC boat .. the KC boat has not kept clear IMO.  

In other words, a ROW boat that has to prevent their boom from moving fully to the port side to avoid contact with a KC boat has executed "an avoiding action" IMO.  

I think this is affirmed in the negative when you read the cases I linked to above.  In those cases they discuss the obligations of a KC boat when equipment is or moves out of its normal location.  

IMO, unless there is a case that says otherwise, there should be nothing unexpected about a boat sailing DDW on port-tack flopping her main over such that she is sailing on starboard-tack. A KC should be keeping enough space between them to allow that.

Brad:  I don't think so.  We have established that the boat on the right in the diagram, boat T, is the 'inside' boat.  She is overlapped.  But she is not a right-of-way boat, as she is the windward boat in the overlap with C.  So she must keep clear under 11.  So she doesn't meet the requirements of 18.4  She also has no need to gybe at the mark to sail her proper course.

18.4 typically applies in a situation like the following, where boat A is inside, right-of-way (starboard tack while B is on Port), and overlapped.

Boat A must gybe at the mark to sail her proper course.  She can sail to her proper course, which is the one she would sail in the absence of the other boat in order to sail the course as quickly as possible, but she can sail no farther from the mark than needed to do so.  [See the definition of proper course]  So in this case, she may swing wide, then sail close to the mark as she gybes, and obey 18.4