Alright. Looks like brass rod will be easiest and will allow me to get these dimensions for each cup.

This should have the optimal nozzle-exit-size to distance-to-cup-base ratio based on what I've read.
But all of these dimensions are variable now that I can simply drill out the hole size I want in whatever rod size I want. The next rod size up is 3/64.
I would also like to thank everyone for their feedback. I'm learning way more than I had anticipated.