When a boat entitled to mark-room under rule 18.2(b) passes head to wind, rule 18.2(b) ceases to apply and she must comply with the applicable rule of Section A.
When a finishing line is laid so nearly in line with the last leg that it cannot be determined which is the correct way to cross it in order to finish according to the definition, a boat may cross the line in either direction and her finish is to be recorded accordingly.
If a racing rule is not one of the rules listed in rule 86.1(c), class rules are not permitted to change it. If a class rule attempts to change such a rule, that class rule is not valid and does not apply.
When a boat's string passes a mark on the required side, she does not break rule 28.2 if her string, when drawn taut, also passes that mark on the non-required side.