Thank you. I have learned a lot as a result of this post.
Related question. Similar to the OP, we don't have any protests or after race rules discussions since we are meant to be a 'friendly' racing club...
Consider 3 boats approaching a windward mark to be left to port.
2 boats enter zone on starboard tack, (S1 & S2).
3rd boat (P) ducks S1 and tacks from port to starboard on S2's lee bow, but within the 3BL circle (P has no mark room).
S1 is sailing below the starboard layline, but has earned mark room that allows her to pinch above CHC to make the mark.
When S1 pinches, she slows, resulting in P overtaking her. Since S1 is both leeward, and has earned mark room, P is forced to also sail above CHC to avoid her.
P is promptly "sandwiched" between S1, (leeward boat to port with mark room) and a S2, (windward boat to starboard that P isn't supposed to take above CHC).
S1 rounds the mark cleanly, with only inches of mark room from P.
There is mild objection from S2 that P forced her to sail above CHC as they (P & S2) tap rails, (no damage).
Since there was contact between P & S2, I guess there was a foul, but I'm not sure who fouled who.
On one hand, S2 was right. P did not have rights to take S2 above CHC. If P is allowed to do this because she is forced to keep clear of S1, P is effectively getting mark room even though she tacked in the zone.
On the other hand, I'm not sure what P's options were when S1 pinched to shoot the mark. P had nowhere to go at that point.