Kim,

In the original post, there are exactly two boats displayed. If we stick to that situation, Blue has heaps of room to avoid, as does Yellow after she tacks. But only for a specific class of boat with known maneuverability characteristics.

As to a "seamanlike manner", one has to specify the boats to even start to discuss this. For many years I raced small and nimble boats that could turn 90° in a boat-length and easily sail dead downwind in a very seamanlike manner. In the original, sailing dead downwind would easily allow Blue to keep clear.  I also spent a decade aggressively racing a 60' schooner that required 120' and many seconds (even minutes in light air) to turn 90°.  In the Original post, if we're discussing my 60' schooner, as Yellow and a similar boat as Blue, then a prudent skipper aboard Yellow would tack far later than is shown in the original post or would be forced by Rule 15 to slow their tack so that Blue could pass.

In the fleet racing situation you've added to the thread, it could be unwise for Yellow to tack into the wall of approaching Port tack boats along with Blue, but Yellow would NOT be breaking a rule in doing that. Indeed, this is a regular maneuver in team-racing for the leader to get onto starboard after the leeward mark rounding and force the competition away from the mark. Thus, it could be a tactical error but once Yellow has established herself on starboard, the responsibility shifts to all the port tack boats. (Again, this would all depend on the maneuverability of the type of boat in question.)

Do note that the question of a "seaman like" doesn't come into play when there is clearly time for Port tack boats to avoid, even if that requires that they head up aggressively, gybe, or even stop. Claims of poor tactics and strategy do not alter the racing rules.

A final comments, NOT related to the original question. You've stated that "In fleet racing , hard luff and crash jibe are not considered seamanlike way maneuvers." First, I'd like to point out that there is no place in the rules that I can find that appears to support this sentence. Both "hard luff" and "crash jibe" could be "seamanlike" or not depending up the boat, the crew, and the conditions. Going back to the dinghy vs the 60' schooner example, it's obvious that knowledge of the boats involved is crucial. You did describe your thoughts were for ILCA and Opti classes. In your diagram, what is a much more likely scenario is that Red and Blue could end up in a pin-wheel around the mark, Green can easily head up and pass to windward of Yellow. Turquoise and Gray have plenty of time to realize that there is a starboard tack boat coming and to take seaman like action to avoid fouling Yellow. I agree that it might be stupid for Yellow to tack into the face of a herd of port tack boats, but Yellow doesn't seem to be breaking any rule.

Right, it was a rhetorical question largely to express my frustration... We apply the rules, we don't "fix" them...  
The recommended wording goes into the documents for any event that I have influence over, but I find the whole situation completely maddening. 

Thanks Paul ... that sounds like a lot of headache. Makes filtering out the daily spam-posts look like a walk in the park. 

If a skipper or crew place their hands, arms, or feet, legs in the water and this action causes the boat to slow down, I believe it breaks 42.1, "a boat shall compete by using only the wind and water to increase, maintain or decrease her speed". Body parts in the water have no exception to decrease speed in 42.3.

I have never given or heard of a Rule 42 penalty given for body parts used to slow a boat. Repeatedly moving the helm is an effective brake.

Phil, How do you conclude that W was not required to act to avoid contact until it became clear that L was not keeping clear?

L was the right of way boat.  She was not  required to keep clear.

W was not entitled to room.