Today I insalled the security cover. All went well with no mistakes. The instructions could be better but get the message across. Thanks to those who responded and provided photographs. It all helped. The cover leaves a 2 inch gap where it meets the edge of the hatch opening. This space is needed to grab the end when latching or releasing, but I would have preferred a tighter fit with a grab handle of some kind.

This was the last cover purchased from the UK!