I've heard people talk about pendulums, and now they can (and do) cause some problems with distance estimating, if you are on a downslope (or upslope - for that matter).

The pendulumcan't compensate for the hypotenuse(?) of the angle if the terrain isn't level. Example: It isassuming that you are 20' in the air and your target is 25 yards away on flat level ground. If your target is 25 yards away on a downslope, then the distance is going to be perceived to be off. ...at least that's my understanding of it.

I like my VBG Camelback pendulum, but might pick up another sight to play with as a backup, in case, for some reason, I decide to switch back to a fixed pin sight. (Mobowhuntr has a cool VBG Pro Slide sight that he really likes).