As I was pondering world peace, entropy, and how to mount a DRO on the Sieg X3 quill, I transcended to another plane...
The Super X3 has a flat milled on the front of the quill. The bottom of the scale is attached to it. The scale is fixed in front of the head and does not move.
My inchoate idea is to make a collar for the quill (2.67" dia), drill and tap it for mounting the bottom of the scale. Take a length of aluminum rectangular tubing and mill off one side of the aluminum tubing of the correct size for the DRO slider, make a mounting base for the slider for inside the tube.
Now the scale moves up and down inside the tube, protected from all but the most horrendous impacts and swarf. The top end of the tube can be closed off with Wisconsin chrome, er, duct tape. Use a parallel to help align the tube. Use some bar clamps (?) to hold the parallel?
Now put superglue on the tube mounted scale, use the parallel to properly align it, and press the tube to the face of the head.