I agree with Ontario. Depending on the diameter of your cooker you could add a couple of "L" brackets and put another rack on top. I did with my old (and long gone) Masterbuilt and it worked beautifully.
In fact, I've been thinking about doing that to one of my WSMs. Then I could easily do nine racks at a time. I just haven't needed to cook that much at once, yet.
BD
