Question: why didn't you just use super-glue or a similar transparent adhesive, on top of the clear film's edge? If done carefully, there'd be no need to melt anything.
I don't like to use glue when working with anything clear.
But like Dr.Argon mentioned, there are multiple ways of doing it. If you're comfortable with that method, I would say go for it. I'm happy with my results, and next time I might even try a smaller soldering iron tip to see if I can get a smaller seam.
By the way, if you have a picture of a case with the film held on with glue, I would like to see those results.
