A while ago I made an n-number plate for my panel, and being bright aluminum with black letters, it was certainly easy to read. However, it just didn't go with the "military look" of the rest of my panel. So, I recently had one made with white letters on a black plate, with a border around it. I think it will look a lot better. The signmaker even gave me some extra copies so I could practice drilling the two mounting holes, which have to match the existing holes in the panel.
Today I marked, centerpunched, and drilled the holes 1-19/32" apart on one of the practice plates. It came out nice, so I will use this plate as a drilling template on the real one.