Premature Optimization
Each shelf has 4 hanging supports. Each support is made of 2 – 12 inch pieces of slotted angle iron. So with 2 shelves left, I needed to attach 16 pieces together to make 8 pieces.
For the first set of shelves, I did this in-place by attaching the first piece to the ceiling mount and then the second piece to the first piece. It worked fine, but was a little slow going since you are working on a ladder with your arms above your head.
I decided that since I’d proved my design worked on the first set of shelves, I could optimize this process.

I measured the length of a hanging support from one of the first shelves and then pre-assembled the 8 remaining hanging supports I would need. To save time, I didn’t leave the bolts loose, I went ahead and fully tightened them with a wrench, saving another step I wouldn’t have to do later on the ladder.
Impressed with my own cleverness, I started to build the last set of shelves. I hung one shelf and then tested by opening the garage door.