they didn't put that curve there on purpose. The bottom edge of the vinyl is actually perfectly straight, it's the windshield itself causing the illusion. Same thing happens with window tinters who don't know how to cut a window film visor that's equal length across the whole width.
I'm sorry, but I don't like how the banner droops down on either side. I mean I know thats how it falls if you use a straight edge of film. I'd go with a rounded shape so when it's put on the windshiels it's more straight across the car. But if you like it thats all that counts.
as long as you like it, thats important. looks good. just not for me. i used to goof on the hondas that have a the H O N D A windshield banner... like nooo!!! we couldnt tell it was a honda, thanks for clearing that up.