i would love to see a rear quarter window louver to match, kind of like what was on the 70s cobra mustangs. it seems to me with the materials and some time, you could just start with a frame built to the inside trim dimensions of a duster/DS rear window, and build it up from there. you could use some kind of "clips" to slide it under the window trim up top, and some sort of lock/clip on the bottom for removal, and to give it smooth uninterrupted transition from louver to trim to body.
