I finally got around to building a Piedmont Water Pan, and took a slightly different approach than most folk here.
First I calculated the circumference of the Brinkmann pan so I could make sure the bolts were evenly spaced (yes, I can be a bit of a perfectionist. BTW, following the circumference of the pan, a bolt every 15.3 inches keeps 3 bolts evenly spaced). I drilled 1/4" holes in one pan only. Using some 3/4" or 1" long 1/4" hardware I had laying around, I placed a nut on the bolt and then a flat washer and inserted through the hole from the top. On the bottom side of the lip, I placed a flat washer on and then another nut. Measuring the amount of bolt sticking out from the top of the pan, I adjusted until there was 5/8". I then tightened the nut on the bottom side of the pan while holding the nut on the top side of the pan. This essentially leaves a "stud" sticking out of the upper rim of the pan that the second pan rests on. No need to undo any hardware to seperate the pans.
I need to try and get pics posted so it's easier to understand.