Smythe - If you cut a 15 lb packer cut in two, it will smoke like a 7.5 lb brisket. That's because the heat surrounds the two pieces like they're in there alone. So, as long as they're not jammed up against each other, they'll smoke like singles. Cuts time a lot! When I smoked brisket in my #1, I would cut a packer in half, right in the middle of the length, then place the thin half on top, and the thick half below. That evens-out the cooking, and never had a problem!
It's best, quality-wise, to smoke a packer whole (if possible), but cutting in half also works!