That's what I like the most about cooking with a SnS on a kettle, it cooks top down, Ribs turnout fantastic.
I believe that's the same with any kettle and the SnS accessory (from now on, just SnS for brevity). As far as my experience with it goes, and as far as I was able to conclude after several tests (read: plenty of briskets, beef ribs and pork butts), the SnS makes the kettle an offset top-down cooker:
* the coals are banked to the side and contained within a confined space with an air gap between them and the bowl, avoiding heat dispersion
* the heat source is moved further up against the cooking grate rather than the charcoal grate down below
* the protein is shielded from direct, radiant infrared heat by the steel walls and the water trough
* all the heat is directed upwards to the lid, and drawn out of the top vent opposite of the coals
The above results in uniform heat in the chamber, as long as you're measuring at cooking grate level. Temps drop considerably below the grate and sensibly increase in proximity of the vent—just what you'd see in an offset, with the hot spot at the collector. While the SnS requires generally more fuel to provide the same temps (as the radiant heat is partially lost and only convective heat remains), the results are more similar to offset-style cooking rather than simple two-zone cooking with the coal baskets.
A stick burner still beats the SnS 5 to 1 but that 1 is quite the difference from anything you'd get otherwise. You can obviously achieve the same with firebricks, it's not black magic.
That being said, I'd be very curious and willing to sacrifice a throwaway lid to try and drill vent holes slightly above grate level instead of the standard ones on top—I wonder, grate level collectors and smoke stacks force combustion gases down and out in offset smokers, perhaps that'd increase the draw and convection for the SnS as well. Who knows. Don't have an extra lid to try anyway.
Guess I got sidetracked. Nice brisket. Looks fine really. Cooked a tiny 9 pounder myself today, overnight cooks beat me down but it's so satisfying having brisket for lunch. Cheers