You wouldn't need to damage it as theoretically all you need to do is slip the cheese wire between the glass & suction cup to break the vacuum seal... or alternatively be a good boy like me & park where you should & for only as long as you've paid for & what clamps are used is moot.
TBH it looks like the answer to a question no one has asked & as others have stated with scratched glass what if you extend that to having a pre existing minor chip or crack there is the potential to extend it when pressure is applied to the glass either when fitting or applying pressure via the suction cups clamping the cups & box edge seal to the glass.
......Really!.......
