Vent in Windshield

Saw or router, both good ideas. You will find the shield cuts easy but depending on who's windshield you have the router may cut to fast and the plastic melts behind the cut. If you saw us a fine metal blade.
As far as a vent goes, I never used one , I just left the hole open
--The vent will look much better with a cover

windshield vent

Randy suggested just cuttilng hole and leaving it open, not a bad Idea. Made me think why not use a hole saw and drill one or more holes, even add a plug if you wanted to close the hole or holes. Gets hot here in AZ.
Terry in AZ.

Sceen Vent

Hi Guy's
I have cut a 5 x 2.5 inch hole in my screen just below the dash level and boy does it make a difference. The push in the back with my Givi screen as all but gone and the air behind the screen is now a lot quieter.

Paul