Marked, drilled, counterbored, deburred, and tapped the Z-motion mounting plate. Unfortunately I accidentally did tapped for M6 screws instead of M5, which are the largest that fit in the linear rail holes, so I will need to drill and tap another array of these outer holes, slightly offset from where I made them. Also, learned that you can depress the drill press and counterbore bit on the edge of the part to set the end stop depth appropriately, see last picture.