I would love see some pictures of the way its setup with the grates.
The previous owner drilled holes through the sides and the existing brackets equal distance between the top and bottom bracket. He inserted screws/nuts into the holes and uses them as holders for a regular 22 1/2" Weber grate. It does make the space between the grates too close to use for butts (except on the top grate).
The additional (4th) grate is a small 18" with 4 long screws mounted to act as legs. It sits on top of the regular top grate.
Benny