I would trust the technology having no first-hand experience, but sheet metal is getting so thin these days that I think you would have to be careful where the cups were mounted. The skin on my Chevy truck is like eggshells. I wouldn't want the skin under/around the cup flexing, not because it will loosen, but due to the potential for eventual cracking of the paint. Of course a single doesn't weigh very much and I doubt that the downward aero-induced force on the rear wheel at 80 mph is all that great.