Great job on your videos and the writeup! I'm going to be rebuilding my diff today or tomorrow most likely.
Question though: Why do you sand the b-fast rings? (or does this only apply to stock?) I thought the reason for their existence was that they were already finished for you, and slick and smooth already. I ordered the b-fast kit for my b4.1 FT and I'm hesitant to attack the rings with sandpaper.