The R5-D4 dome I purchased uses holographic gift wrap paper as the reflective material in the neck rings slots. While there is a little debate as to what was actually used on the R5-D4 dome in A New Hope, to my eye it looks like engine turned aluminum in the reference photos.
Years ago, one of the local R2LA guys offered strips of engine turned aluminum, suitable for the neck ring rectangles on the R5-D4 dome. I acquired some, and needed to cut the rectangles to the proper size.
I went into work to abuse the office paper cutter. There are sixteen of these aluminum segments to cut. They are approximately 1-11/16" x 2-7/16", but each one needs to be cut to the exact size of the corresponding "window" in the neck, as the spaces vary ever so slightly.
I cut each piece slightly large, and then trimmed it to size as I iteratively fit and cut the piece to match its spot on the dome. I numbered each piece as I went.
After about two hours of this, I had all sixteen pieces cut to the proper size.
Along with a bunch of scrap.
I plan to use 3M VHB tape to attach the panels to the dome, after I remove the holographic paper. I am debating whether to drill small holes behind the panels so that I can poke them out from the inside of the dome, if I ever need to remove them for dome repainting. I probably will drill the holes.