[Evans, Marv]

If it were me, I would also go with replacing the original sheets as needed. I would drill a hole for each place I wanted to place a screw (if that's possible in that material without cracking it) and put in a hex head screw that comes with a washer with a rubber or neoprene washer under that (HD or wherever). A little silicone maybe wouldn't hurt either. I don't have a strong opinion about putting them in the ridges or valleys, but I think I'd go for the valleys to keep the amount of flex to a minimum & be careful about not over tightening the screws. Five years isn't a bad amount of time for a structure like that.