I recently acquired an 18.5" WSM and found a 16-inch clay saucer which I'm going to use in place of the water pan this weekend for a butt. I really hate the shape of the bowl on the 18.5. I suppose I can always put an aluminum pan on top if needed.
Weber Performer * Cajun Bandit * 18.5 WSM * WSM Mini
Donated the Weber OTG and modded Brinkmann Gourmet