This weekend I attended a Match Race Training for our National Talent Team. But instead of sailing today we spend the day in a class-room setting, going over cases, rules and tactics, because the wind was blowing to hard to go out on the water. WindGuru predicted a change around noon, but it never panned out.
One of the discussions we had, was about the uncertainty factor of proper course
In the following diagram Blue and Yellow are on the downwind leg of the course to a gate.
Yellow to windward has to keep clear under RRS 11. Blue - having established an overlap to leeward within two boat lengths - may not sail above her proper course under rule 17.1
In position two Yellow calls with Yankee because she wants to go to the SB-end gate mark. The umpires answer with Green.
In position three Yellow again shows the Yankee-flag. She has reached lay line to the P-end gate mark and wants to gybe. Blue should not sail any further and gybe too. Again the umpires signal Green.
Umpires always operate under the basic principle that they will green flag any incident, unless they both are certain a rule has broken. In this incident Blue- the r.o.w. boat - has not yet reached her lay line to the P-end gate mark. Therefore she is not sailing above her proper course and not breaking RRS 17.1.
The uncertainty of the exact lay line will grow depending many factors. The first one is the distance to the gate. The further away, the longer Blue can continue in this position
Only when the gate is very close and there is no doubt that Blue "oversailed", will she get a penalty for breaking rule 17.1
Which gate-mark is going to be used to determine the lay line - even when the SB-end is positioned favorable - is not something umpire are willing to decide.
Knowing all this, what should the answer be from the umpire on Yellow's Yankee in position four?