I cover my polycarbonate windshield because mine was cloudy when I got the boat. Replacing it was a nightmare because you need about 6 or 8 arms to fit the flexible sheet between two curved frames. I don't want to have to do that job again anytime soon.

BTW I was told by a well-known plastic hatch insert replacement company that the UV-resistant version of polycarbonate has a UV shield film bonded to it, and that the film tends to delaminate when the piece is bent such as my windshield. He also said it scratches even easier, so I got the standard non-UV rated version. I had a cover made and so far it's looking good after 5 years.