Chisox post made me think of one other thing FWIW.........I always try to put the fat facing the heat source when possible (fat down in WSM) so if something happens and the heat gets away from me I have more protection for the meat.
thats what I had heard, so I was going to give it a try. Even though in the 20 or so smokes I have done on a WSM I have noticed it holds temps in the low and slow range masterfully. Thats why I had to have one of my own.
I have never flipped pork butt, using a water pan in my GOSM I get pretty even heat, no hot spots to worry about. I have done it fat up and fat down and not seen a difference.
Good luck and remember to Q view!