I used to use the mylar over 35 years ago. We didn't have diskettes back then but we had mylar for use in our paper tape readers and punches that served the purpose. I remember using two pieces of material to form a trailing edge with the mylar sandwiched in between. I really didn't trust the glues to stick to the mylar so I used the computer to punch a "5252" pattern in the tape so the glue would tend to form miniture rivets. It worked quite well and I never had the mylar rip, not even in a crash. It also sealed the hinge line, of course that wasn't a consideration for me back then.
Now that you have me thinking about it, I'm gonna see if I can find some more of that stuff. I used to have suit cases full of it as we used to keep programs on it. Yes back then programs were kept short!