Thanks Mark.  In this case what should red do?  Can they not round the mark and protest/seek redress or do they have to tack around and find a space behind the pack?  Surely, somehow turquoise should be penalized unless she is somehow restricted by an obstruction.  Appreciate your advice. Ben

Well it's tactical advice rather than a racing rules answer, but maybe gybe and try to stick it to Yellow before the zone, get Yellow to gybe and maybe create enough room to get around on the inside.

Otherwise drop kite early, fishtail like crazy to lose speed and follow Yellow around on the inside line.

Do not go around the outside 5 deep.

An anecdote from a long time ago as an inside boat in a somewhat similar situation - Class 1 started on a beat, as we approached the "windward" mark, the wind died.  Class 2 started 10 mins later.  The wind filled in behind, so Class 2 hoisted kites and mostly headed into a line of stationary Class 1 boats, which hadn't yet got the wind.  There was a lot of shouting!  The boat that won out of all the mess was the one that did go round the outside of both classes - although sailing further, she kept moving in clean air and was off on the new beat whilst the rest were still shouting and pushing others off.  (I don't recall what happened in the protest room.)

Tim,
If Red gybes onto starboard she acquires RoW and under RRS 15 she must allow Turquoise room to keep clear of Green, Green room to keep clear of Blue, Blue room to keep clear of Yellow and Yellow room to keep clear of Red!