Here's a mod you don't hear about very often. Remove the chimney, and weld the gap between the flange and the chimney, closed. It really helped level out temps in my NBBD. I had originally used JB Weld, but it eventually failed.
Looking forward to how your brisket turns out.
22.5 OTS(H), 22.5 OTG(DA), 22.5 Daisy Wheel Kettle(EE), NBBD, UDS, MUDS, 6-burner gasser