Yes, having initially chosen to drop Y from 32, I eventually opted for S, in the interest of readability. 'Thin fish' definitely suits Y better, and doesn't suit G.
I've just seen the alternative for T in 5. Makes sense now. Thanks Dryden.
I think 'slender beaked head' in the Chambers entry for the full version of the fish justifies it. 'Thin' should have alerted me to reconsider my first choice of S because I wouldn't call a bream thin.