Grinding the pad to use glue is a VERY BAD IDEA!!!!! and it is done all the time. You risk breaking the windshield during rapid temperature changes. The foot is too large to be glued to the windshield. When Porsche started gluing the foot to the windshield the contact area was a much smaller circular disc. I have sold many windshields to people that thought glue was a good idea. True, the double sided rubber pads sold by Porsche and many aftermarket suppliers were simply cut from a 3M product.
Pro tip #1: The tape always had different colors on either side. One side was black. The "colored" (red when they were first introduced) side always goes against the glass.
Pro tip # 2. Buy two or three and put the extras in your glove box. You will need one upon the change of seasons.
Pro tip #3. Don't grind the edges off!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!