Race rules...

If those 4 boats all line up nose to tail from the mark to make their rounding, then green is overlapped with red when red reaches the zone.

Anyone lined up bow to stern with 3 boats between them and the mark has to give room to pretty much everyone still coming down the course.  Don't put yourself in that situation, and if you see it, take advantage of it!

3 boats in front of them could be a tough argument in the room.  4 is easier.  5 is a slam dunk.

Interesting to know that. It would also depend on how 'significant' the advantage would need to be. I would not say that staying ahead after turn could be considered significant, the other boats may have decided to have a luffing match and end up stopping. 

It is a subjective thing, who can persuade the PC.....

Can you expand on the Jim? I do not see that as part of case 63 anywhere.

If green (in this case) gets it wrong and infringes any of the other boats the penalty as defined is a 2 tack 2 gybe (effectively 720).

The only way a retirement could be forced would be for one of the other boat to protest them under rule 2 which would be a bit harsh.

Green should be on standby to either bail out to avoid infringing or be prepared to take a penalty if they do. Yes it is a risky thing to do but it pays off more often than not in my experience.

The rules do state contact should be avoided where possible and you should give room and protest.

Red could leave themselves open to a protest against intimidating behaviour depending on the nature of the shouting as well.