I've caught a few of those big san juan crabs. Lots in the 8-9" range and a few over that. Our biggest was a little over 11 inches and it had what appeared to be purple paint on its shell. Still tasted fine to me.
Another crab question: has anyone caught any tanner crabs (like snow crabs) or puget sound kings? We caught 4 tanners in the san juans in 12 fathoms over a muddy bottom. They were only about 3 inches across in the shell but 8 or so in the legs. We let them go since they were small. Anyone get any big ones?