Seems fine. If you don’t need to see out that part of the window you could just put the flap in a piece of plywood. Check the scrap bin at Lowe’s for one that’s close to the right size. Maybe put adhesive weatherstripping around the edge to hold it in well.
How did you net it? We have a small side yard that’s fenced/gated. I’ve been wondering how i could cover it to give my kitties a play zone.
That’s a good idea. I bet i can find pics or videos.