The vented windshields, that I have seen, have slots running vertically on the lower/ middle portion of the windshield. A Router would be the tool that I would use to duplicate the patterns of slots made on the commercial vented windshields, referred to above. Perhaps, you should do a Google search for RZR vented windshields, etc. and see the designs that others have used.
I have not seen any windshields with holes around the edges, as you purpose. Perhaps the reason is because of improper air flow or pressure factors caused by such a design.
RJ