A hard-to-remove sticker on the windshield for parking in the wrong place? Won't that guarantee that the car will be staying in that wrong place for a lot longer? It doesn't sound safe to drive with a sticker in the middle of your windscreen.
This is just plain destructive and counterproductive. Use something that's easily noticed but also easily removed.
This is just plain destructive and counterproductive. Use something that's easily noticed but also easily removed.