I have a 51 chevy that I choped 6 inches. I had a ploblem trying to find someone to cut my glass till I talked to a old glass guy and he told me to use a belt sander with 60 grit paper made for glass. The paper is black in color and it worked great. It took me about 4 hours to sand down each one but I didnt crack them. Just take your time and go slow dont push on it let the sander do the work.