Just did one that size with water on my 18.5 on a breezy overnight. Started it minion with as much unlit as the chamber would hold. (You have to sort of "concave" the fuel load to not bump the new big water pan.) About five fist-sized apple chunks. Had to add about a half chimney (lit) near the end. Keep tappin' those legs. Mine is happy at around 240. It took a good 18 hours. I foiled the last hour just to hurry it up a bit. Finished at 200, sat in the cooler for about 2 hours. Pulled nice and went down great with some homemade slaw, some Franklin Barbecue Sweet Vinegar sauce, and of course, a few Shiner Bocks.