On a long rappel (generally any rap over 200 feet), the wise canyoneer does not expect to use one friction setting all the way down. The weight of the rope (about 30 lbs, when DRY) means that in order to make progress on the upper part of the rappel, you will need to set the friction on your device at "low". Perhaps every 100 feet or so, you will need to make an adjustment to add more friction. Basic info on using a Pirana is available here: http://www.canyoneeringusa.com/techtips/how-to-use-a-petzl-pirana/ Same thing for ATC: http://www.canyoneeringusa.com/techtips/black-diamond-atc-rappelling/ Going over a top horn on the ATS or Pirana ("3" setting) is a BAD way to add friction. In this case, it is not a question of morality - it just does not work well. The accident in Insomnia (Arizona) was due to "going over the top horn to add friction" or, really NOT doing so, missing the hook, and losing control in the process, cratering in from about 100 feet. Thankfully the guy on the ground got it all on camera... though perhaps a bottom belay would have been a (morally) BETTER choice for the guy on the ground's attention. But I digress. As many have noted, the point at which to add friction is BEFORE you are out of control, while you can still stop and do stuff. Hard to judge in the sensation overload of being IN a waterfall. There are several ways to add friction, but my favorite system is to go to a left-leg loop carabiner as the first adjustment. In private, this is referred to as a "Lap Dance". I am right handed, so from my EXTENDED rappel device, the rope goes across to my left leg loop (carabiner), then across my lap to my right side and over my thigh. Then I can vary the amount of friction produced by rotating my hips. Rotating toward the rope straightens out the rope path reducing friction, while rotating away from the rope path runs the rope over more of my hip and thing, increasing friction. The rope can be clipped into the "left leg loop carabiner" while you are dangling in space - one of the subtleties is that it is very difficult to bring the rope to the carabiner, it works much better to rotate the hips and bring the carabiner to the rope. Plus getting the rope in place is much easier if the belay device is extended. The next phase in the system is to convert to a Z-rig. A carabiner is added to the eye of the Pirana, or the slot of the ATS, and the rope is clipped into this. Thus the rope goes Pirana/ATS to Left Leg Loop Carabiner, up to carabiner in the eye of the Pirana, down to the brakehand (and the ground). Which has additional friction over the Lap Dance. It takes a little getting used to, so it is good to practice. No, you don't have to find a 500' cliff to practice on, only a reasonable size cliff with a buddy down at the bottom to adjust the weight of the rope for various situations. The better, more adjustable system is to use a caver's rack, but then you are just overwhelming the problem with technology and where is the fun in that! Comments? Critique? Questions?