Just thinking out loud...some manufacturers that laid mylar around pops had openings larger than the skirts, leaving an un-protected ring around the skirt.

Maybe put the mylar down before installing the pop assemblies...so you can "underlap" the skirt?

Raised stud nails or whatever the pop mounts are called can nick the ball and cause wrinkles in the mylar. I guess just make sure they're hammered down flush.