I have the much flimsier first gen fiber board cover. It was able to support my 70lb greyhound with some deformation, but no real worry of breaking. I did cut out a 3/8" plywood blank that I can put over the hole. But haven't really ever needed to use it.
I've asked at the service center for a cost on the new plastic cover. Like jerry33 says, it looks to be able to handle anything that isn't going to overload the car. But they haven't been able to give me a price.