I admit to using the PC lever without the chain hanger when I raced in the early 80's. With the PC lever I was able to lock-out my 12t descending cog. This was a good thing because my best sprinting cog was the 13t, and by locking out the 12t, I could slam the shifter forward in a sprint without worrying about overshifting onto the 12t. The 12t was still available when I needed it on descents.
Kevin Ko
Eugene, OR