Hopper Windows Protection for Cats

Reading this it will get clear that a protecting grille for hopper windows is a must have for cat owners.
This is my first try to make this protections by myself. It is designed for standard windows with a gap of 16cm on the upper corner. Because I have plastic windows I can't use screws. But with thin transparent double sided adhesive tape by 3M the grilles stick strong enough on the window. The foot of the grille will be pressed to the windows frame by the seal of the closed window if it is m