Has anyone ever used a mounted rear sight with a pendulum (Keller). I am getting tired of the old peep sight but like the keller too much to go back to pin sights. I can find all sorts of rear sights for pin setups but never see anything on the pendulum design.

David, I shoot with a savage pendulum sight but do not use any type of rear sight, not even a peep. I line up the pin behind the string.
try it, you will be surprised at the results.

The reason a rear site works is that you always line up on one pin, I always used my 40 yard pin to line the rear sight up on it.
if you have a pendulum with only one pin it won't work because the pin moves which means you would have to change your anchor point with each shot depending on how far away the target is.

If you had a pendulum with some fixed pins also like a toxonics the rear sight might work if you always anchored and lined up on one of the fixed ones..hope this helps ya.....