I wonder if you could get a pair of daisy wheels from Weber on their replacement parts website. Install with spring screws over eight half inch holes. Your exhast would be spaced out if you put them across from each other and you could easily shut them down, no nipples to hand close.
EDIT: Big Poppa Smokers UDS kit is currently out of stock, but when they get parts back in you can order daisy wheels from them as well. I believe their version uses eight 3/4 inch holes.
~ Scott ~
Blue Weber Performer + Craycort CI • Brick Red Weber One-Touch Platinum • Weber 26.75 Kettle • Akorn Kamado • ET 732 • Record-crushing ORANGE Thermapen • UDS In Progress