With the drilling completed, it's time to countersink the holes in the windscreen for the countersunk attach screws. Make sure you do the countersinking before enlaring to 5/32 so that the pilot of the countersinkcage has grip and avoid wandering holes.
As you can see in the image below, my pilot holes are still #40 here while i'm already countersinking. this required making some test drilling to get good countersink cage dept prior to starting the work.
As the screw can't still be inserted in the hole, there's no way to verify depth with the real screw until you open up the hole to 5/32".

Couple of holes done.

Next enlarged the holes in the plexy to 5/32". First updrilling with an acrylic drill to #30 and then using the 5/32" reamer to finish it of to a silky smooth hole.
As you can see, great alignment as well.