My 63 falcon squire wagon has a flat rectangle glass rear window. Recently the electric motor fried. It was stuck down. It was snowing. I went to the hardware store and picked up some lexan. At first it felt like plastic. I got some angle aluminum for bracing to keep the glass from flexing and pushing out from the wind. While drilling for rivets, I drilled through the lexan first then through the aluminum, no problem. I eventually switched sides and started drilling through the aluminum first then through the lexan. The lexan cracked when I pushed through the aluminum. It is very small and hasn't gotten worse....yet. I used to think it was easy to work with. I might make my own lexan windows someday, but I'll be more careful next time.