I installed adhesive felt strips from Durofelt on our TL 5 years ago and haven't had scratching or adhesion issues since. I would buy again with confidence and the price is right.
As long as the window seals are clean, you won't get scratches, but who has the time to check and clean the window seals. Putting on the felt was unnerving the first time, but it is insurance that your tint won't get scratched.
Durofelt
BTW - i didn't bother to felt or moleskin my e90 after tint.