Below is a chat from Raybestos. I would seem to indicate that the clips do work and that repeated braking also increases drag. The lower line represents with clips installed. While they claim a 49% reduction in drag in the first 10 seconds, there is no indication of the overall reduction. As this is from a sales brochure it probably represents a best case.
Looks like Redneck posed about this back in post # 23
Link for complete PDF
http://www.raybestoschassis.com/wps/...1df63649a75f53