Oh that is beautiful. For some reason I always called it the mizzen ballooner. I don't have one, but I wonder if the sizing should make it higher cut, so that it has to balloon out, preventing interference with the backstays. Everything I've read seems to match your attachment points.
And +1 for the oxiclean. I used that and a pressure washer, but letting it soak would probably be less labor.
And +1 for the oxiclean. I used that and a pressure washer, but letting it soak would probably be less labor.