Ribbons have bad vertical dispersion. If you can put them into a-pillars you may be able to get them to work pretty well, but other than LCYs the vertical off-axis response is TERRIBLE (which makes them good for kick panel mounting but then the back passengers will hear nothing). You'll have to sit in the same position and not care about passengers' sound. They're also generally expensive and very large (my AC G3Sis are 5.5" x 3" with 3" depth). They don't need boxes, they're tweeters with sealed backs. If you're looking for some ribbons, I am thinking of selling my G3Sis (they're AC's middle range - list price is $500/pair and $425 online - I'm obviously not looking for near that - I'll stop plugging them now). Basically, they can sound great but are hard to integrate into a car.