17 crits look solid. I'd mix fanatics with lavamancers or other fun 1st turn drops like shadow guildmage (Die Bob! Die...). Keep people guessing and throw them off balance. With the addition of Tarmogoyfs in opposing decks, I bring some stingscourgers in sideboard. FTKs (most of the times) fail to kill a fat goyf. Spell snare is definitely good for countering these specific threats.
But Fish decks, including urbana, are metagaming decks IMO. 3 REB main deck may be a metagaing choice... So telling us your meta will help us help you

Hope that helps.