In this situation I would deploy the "slow down and win" tacktic. Slow down the boat let F and D pass and dive around the mark behind them and Gibe to a Port Tack. While hoisting the spi sail to below F and be rid of all downwind boat from then onward as I'll be sailing faster and deeper with the spi. The other spi boats are not much of an issue as they sail as fast and as deep as me and have to do the same thing in gusts.

The only drawback of this scenario would be that I could encounter SOME boat going up to A-mark sailing on a port tack. However! This is not a big risk as never alot of boats approach the A-mark that close on a port Tack. Often only 1 or 2 boats try this in larger fleet and it should be enough to spot them (skipper) when you are hoisting the kite. You will see quickly enough wether they are close enough to meet you or not. Most other boat going upwind will either have sailed trhough the middle or over the starboard side of the course and approach the A-mark on a starboard tack from quite a distance away.

So in principle you are not really in a jam yet.

Wouter