Hi Jared, I don't know about carpeting, but as far as the new rail goes, I drilled new holes, just because its not easy to see the old holes because you are covering them up with new rail! Make sense? I got a cheap rivet gun and 3/16 rivets and went to town. It was kinda fun after awhile drill hole, insert rivet and "pop" them tight! I just figured out a pattern so I didn't accidently drill into any existing holes.
Hope this helps you!