I just installed the type II CF performance spoiler on my e90 yesterday only using 3M tape. Worked perfectly and definitely will not fly off (even if you go 100+). I don't understand why everyone thinks you need to use permanent betalink.
I didn't even use a heat gun or anything. I just lined the spoiler with 3M a bit back from the edge, lined it up with the trunk, and stuck it on. No tape is visible.