didn't have a rock guard when I bought it. When driving into a hard rain I was getting water in through the front window. They're old and the crank will unwind slightly during driving allowing the slats to lose they're seal.
I had a local machine shop weld a 3/4" x 3/4" aluminum frame, a shop in Michigan make a custom aluminum 52" offset aluminum piano hinge, bought hood struts on Ebay, and used a half sheet of fiberglass roofing for the covering. The covering is attached using self tapping metal screws. A latch is attached to ensure it stays closed.