Hey,

I have been testing UBW fish for some time now and my best recomendation is to consider running ethersworn canonist.  If you are really concerned about goblins and elf being at GenCon which I assume they will be, she would be a great addition to the team.  Doesn't hurt your deck very much.  Cripples elf ball and is amazing against most other combo decks.  It is also good against Tez.  I am not saying that canonist is the ultimate solution but I would recommend her.

I have plenty of suggestions but without drastically changing the deck this is my best one.  Canonist and meddling mage also work well together because it gives alot of decks two cards they need to deal with.

One last thing.  Fish is a great budget deck but I would definitely recommend that you find yourself a way to deal with aggro decks.  You don't really have any meat in the deck and random aggro will most like run you over.  It is tough to tell you to just throw in a few cards in the side as a solution but if you do cut the enlightened tutors.  For GenCon I would definitely expect more aggro decks than the average tournament.  Best of luck and I may run into you at GenCon.