I used to install them when I worked at Toyota (back in the day)onto supras, celicas, even corollas and tercels.
They usually made rattles and buzzing after a year or two. The paint faded. Brackets came off. etc etc.
I do like those other ones that are about 8-12" wide, and mount at the top of the window, for air spoiler effect and shade.
Check out this site. But you can't see a good shot of the piece I'm talking about.
http://members.aol.com/akiraneo/kits.html