Jake, the seafood racks are great (I have one), but if you want to save a bunch of $, for the occasional smoke that you don't want to fall through the cracks, get some Q-Matz from Amazenproducts.  These are washable mats that you can order to cut to size.  I use them a lot, and are substantially cheaper than the seafood shelves.  The fan is the only other essential!