If you use ABS you must cut air movements from outside. For the Abs to stick to the surface, keep the pure acetone and a piece of natural abs filament in a container for one day and apply the film as a thin layer to the surface while it is cold and wait for its drying.
My front window has 28cm width, 34cm height and 3mm thickness. Clips designed for this dimension and there is no tolerance. If you cannot fix the window you can use sandpaper.
(My advice is 50% filling)