Now, the LE Rear door flare doesn't line up with the rocker trim. It's fine for the time being. I have a hunch that the 2014 door section of the rear flare will line up with the 10-13 LE rear quarter section. I traced the profile of the 2014 rear flare on a piece of paper, it appears to line up. The part is around $50 each side but it comes unpainted. Eventually I may give it a shot, we'll see:
You mention that the rear flare extension doesn't come painted. Do you know if it is black plastic like the forward extension or a different finish altogether? I would have guessed the former to match the rest of the rocker trim.