Charles, you are correct about kerning. I was in the news business and had to learn typography. The circle format accounts for kerning. And for that reason, transferring the reversed letters from, say, Microsoft Word or Publisher, onto the circular sign would take that into account. If you used an outline font, your hand cuts would require that you lock the workpiece support down at variable positions for each letter. Trying to recall what Barb uses to transfer the laser printer image to the sign. Some sort of mint oil. Maybe she'll pop up.
In the old hot type days, and even cold type for headlines, we had to count the size and spacing to make sure our headlines fit. I, f and t got half a count, most other letters got one, Caps got 1 1/2 Cap M and W got 2 and spaces got one. A 36 pt font, depending whether it's condensed, you could fit only a certain count per column, adding an extra for each column. The idea was to have headlines fil the full width of the column with not a lot of space left over. It was an art. I was news editor and placed the stories and wrote most headlines for the front 5 pages. An assistant did the inside sections. Kerning is changing the space between letters so they fit together in an attractive way. It affected readability. 72 pica per inch, we all had "pica poles" nearby.
Sorry, got carried away there.
I think most people are better at moving a router to the right and down for signs, and this would allow that on circular signs. Certainly not for everyone, but this jig would help a few of us do a better job on lettering and allow making something different.
The more I do, the less I accomplish.