Good info! But I've been breaking all of your rules. I tried a water repellant for the top but it was a mess so I abandoned the idea. It even stained the trim between the window and the door (left speckles). If I do it again, I'll treat it like it was paint and mask the car completely. I've also got the wear spot behind the rear window, but I'm out of the coverage (2008 128i). I'll just keep an eye on it and do more research on how to fix it. Even with all of this, I love my convertible. I don't think I'll ever go back to a "fixed head".
The 3M glue comes in tomorrow and I'll give it a go on Sunday.
"Nobody gets in to see the Wizard, not nobody, not no how!"