I have had the car up to 110 blowing out the carbon and no problem at all. Usually its a back country road at 50-60 and around town, but driven at a steady 70 to 80 and never a problem. Our windscreen came with the car and gratefully the holes weren't drilled. I have all the original parts. I don't believe in unnecessary holes etc if I can help it.. 57,000 miles and counting.