When using an offset stick burner (most of my life) I always smoked brisket and butts fat side up...with the brisket point closest to the firebox side. And, I even installed baffles in my stick burner, which gave me an even temp across the grate. But, it still seemed to always cook faster toward the firebox...so, whatever I was smoking, I put the thickest side toward the firebox. And, with brisket, I always smoked fat side up, as the radiant heat source was never always from the bottom up, as it is in a WSM. The radiant heat in a stick burner would leave the firebox, enter the cooking chamber and go straight up, then end up coming back down on your meat. While the smoky convection heat, that is doing most of the actual cooking is swirling all around the meat. And, it made sense to me, since a lot of the radiant heat was coming from the top, to let it hit the fat on top...and that melting fat would roll down the outside of the brisket...and most of it would roll down the flat, and seemed to keep it more moist on the outside and acted as a baster or spritz. And, that's the way a lot of the old time Texas barbecue joints smoke their brisket. However, with the WSM, the radiant heat source is directly below the meat. Now, this is not the smoky heat that is rolling all around the smoker and doing most of the cooking. Radiant heat runs straight up from the heat source and heats anything it runs into. So, for my one and only pork butt I cooked on my new 22.5 WSM, I smoked it fat side down. I'm going to do my first brisket on my WSM this weekend, and also plan on smoking it fat side down. That way, the fat cap will actually protect the bottom side of the brisket from the radiant heat. But, then again, I think if you're going hot and fast it will make a bigger difference than if you're going low and slow. So, who knows!
