Anyway, confirmed that A5 is shorted to the innermost PR pin, and ground is shorted to the outermost PR pin. I made the connections and tested with Candle, I can z-probe. Now playing with the height map.
It may be possible if your material is very consistent thickness, as you can mill a base to be flat and then place it on that. It would be easier to use a floating bit but this requires more specialized tooling.
I'm still not clear what you are trying to achieve, a scratch in the surface or some filled engraving?