The correct method is to fly the S flag with two sounds, period. No prior signals are required (or advisable, just adds confusion).

The most fair method is to anchor to the left side (looking upwind), setting a line that is no shorter than 6 lengths (mark room on both sides), and is square.

The ideal method is to use a leeward gate, and fly the flag close to one of the gates (so you can call close finishes and no one tries to finish between the mark and the boat). PU taught me to tie up to the mark's anchor, with the mark alongside the boat, or even in it.

The redress in this case sounds like the fairest arrangement given the circumstances. If the RC still thinks they did the right thing, walk them through a scenario where a boat would hook the mark while another comes in under spinnaker, finishing per the book...

Hope this helps.

Mike