I have got perspex in the rear quaters at the mo and its fogged after very short use. I spoke to someone who has had poly carb for over a year and its still clear with no scratches or fogging. there are pics of a civic type r on the website that has had a prang and the panel that is hit is caved in and the poly carb is just out of shape. He cut it out and re fitted it after it was repaired no issues.

http://www.acwmotorsportplastics.co....page=page&id=4