For drilling the holes, I used a sharp scribe from a protractor to mark out where the holes should be from the old plexi, then used a ruler and measured 1/2" (or half of whatever) in 2 directions for each hole, resulting in an X and marked where to drill perfectly.
I used a drill press to drill out the holes, and what I did was to lower down the bit with the drill off, make sure it was lined up, press the bit into the plexi a little to make a little indentation, then fired up the drill and make the hole.
I did a full street fighter panel for a 25" Dynamo!