When I put them on my old 3.0, I trim off all the tabs and use small screws to attach them to the plastic arch and bumper. No problem for couple years. That's the way Tom (mrbmwX5) put his on also, for many years and miles.
I remove and sold them separately, before I sold my 3.0. Only left a few tiny holes which hardly noticeable. I will get a couple screws to secure the flares on my 4.8iS. There are reports that they flew off.

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00 E39 DINAN S1 //M5 (82k miles)
06 E53 DINAN 4.8iS, born 2/18/2006 (126k miles) http://www.xoutpost.com/bmw-sav-foru...s-my-dslr.html
90 Straman Z32 TwinTurbo Convertible, (1 of 44 ever made) 5 speed, 444rwhp/451rwtq
01 360 Novitec Spider F1 (26k miles)