Originally Posted by ScottK
Well I hope not, I just drilled mine on by eyeballing the alignment. The handbook section 8 (8-14 in mine) talks about this, and refer to drawing 38 for the arrangement of mating bracket F-996A. It's drilled to the fuse in assembly, so any alignment roughly vertical to the floor ought to be fine.
Eyeballing is probably fine. My mistake was I didn't consciously eyeball, and then during the drilling the bracket slipped a bit. I didn't realize it until it was too late, making it about 1/8" out of vertical from one side to the other. At $17 to replace the rib, it's worth it to me to not end up with a finished tank that then has a bracket that is impossible to use.