Cracks! Nobody likes cracks in their windshield! I think that's why the use this method on their windshields now...
Many years ago, during the development of the clear fairing, National Cycle found that ordinary drill mounting methods caused stress cracks and eventual breakage of acrylic shields. That's why we developed and use our patented No-hole Ballsocket system on all of our acrylic products.
Anyway I'll let you know how it works out this winter.