This video seems to indicate that you can bend U channel, although he doesn't actually show the bending process in action.
https://www.youtube.com/watch?v=22PqMv1fQ9w.
As far as the vents go I would stick with the 4 slats and reduce their width a little. Going from 4 to 3 is a lot more obvious than going from full size to slightly narrower in my opinion.