I did drill a hole earlier this week before leaving town to make sure the build 9 worked. I do not remember the exact dimension that i found from the CAD files but the number that I do remember is 71.x mm from the front edge of the HL2 board. For both of my units I put a piece of masking tape on the bottom underneath where the hole was and used a large C clamp to hold both boards inside the case. Used a drafting pencil to fill the circle on the masking tape then drilled a small pilot hole with a pin vise. Turn the case over and use an 1/8" drill in the drill press which usually looks like it just burnishes the inside rails.
When I used the CAD files to find the hole location I was surprised to find the origin (0,0) a large distance from the rest of the board. From a DFMA view there is usually a tooling hole inside the actual board, but not a corner. The top left mounting hole would be great if you like 2nd quadrant dimensioning. This location puts 3 holes on the primary axis's and minimizes the cumulative tolerance to the board edges while making a smaller error for Pick & Place,step and repeat paneling and case mounting as the drill file is way easier to read and find holes. This made finding the 9mm a bit uncertain so I just used the tape & drill method above. If someone could do a mechanical drawing of the hole location on the outside, that could help.
Just my penny's worth.
Dick K9IVB