Hi Mike,
I would like to help you with doing this if I may based on my experience.
I did exactly as you are planning to do and there is nothing to it.
See pic of my bike below.
Here is how I drilled and attached mine, and I never had a crack in the windshield from doing this.
I drilled and mounted three leather bags to my windshield.
First, I gave my wife a black fine point marker. She stood in front of bike facing the windshield.
I sat on the drivers seat and held the center bag in the center of the windshield and lined it up by eye from left to right top to bottom, and got it where I wanted it.
My wife would just touch the front of the windshield with the marker, in the center of the mounting holes thus leaving a small dot for the location.
I then held the right side bag, she marked holes again, and then I held left side bag as she marked those holes.
I then placed a DAMP towel on the dash to catch the small pieces of plastic (chips) from when I drilled.
How to drill the holes.
DO NOT PUSH the drill into the windshield.. Did I mention that you do NOT push the drill into the windshield...
Here are a few notes before you drill anything.
Use a small variable speed hand drill (cordless if possible) for better handling and less to control when it comes to tangling the cord, or tripping on it.
I did not use any tape, but you can if you want if you feel more confident in doing so.
Let the Drill bit do the work- do NOT push it thru the windshield..for it will easily go into and through the plastic almost entirely by it's self.
Pull back on the drill as it drills the hole so that the chips break off and are channeled out thru the flutes of the drill bit.
Drill very slow speed....very slow.
You must first, Drill the mounting holes using a small drill bit. Reason for this is if the hole does not line up exactly in line with the mounting holes in the bag, you can always PULL the hole to the direction you may need when you use the full size drill bit..
Drill from the front towards the drivers seat as you straddle the front wheel
Once you drill the mounting holes for ONE BAG, stop and make sure the holes line up
Do NOT drill the mounting holes any larger than the diameter of the mounting screws you plan to use. Mine were a snug fit and I never ever had a crack or issue with mine.
Provided all the windshield holes line up to the bag mounting holes, you now have to drill the holes full size. Again, the same size of the mounting screws you are using.
To mount the bags.
I used black Dome head Allen screws (which blended in with the black bags and you could not hardly even notice them), and I used CHROME acorn nuts.
I pushed the screws into the windshield from the FRONT of the windshield, thru the leather bag.
I used a dab of BLUE lock-tight and then attached the chrome acorn nuts from the inside using an Allen wrench to hold the screws. NOTE: DO NOT OVERTIGHTEN..I used my fingers to hold the acorn nuts. Once the nut turned in my fingers using the Allen wrench from the outside, it was tight enough. They never came off and I never hand an issue.
Good luck!
Here is the pic of mine: