This is a subject that has gotten a lot of attention, the thing about grip is that there really is no right or wrong. I started like a lot of people with my index finger out on the rim of the disc. I was corrected and told that you need to have all of your digets under the rim, and since the power grip never felt right I too went to a stacked fan grip. I can throw a disc fairly far down the fairway so I do not think that power is an issue with that grip, however recently I have been doing some modification in my game overall and I notice that when I drive the "rip point" of my grip is towards the tip of my index finger right where the knuckle bends. The problem for me is that area is mostly bone and as the wing on discs gets wider they seem to get sharper and tear that part of my finger up, so I am transitioning to more of a power grip where the rip point is still on the index but in between the first knuckle and the second on the meat of my finger.
IMO the grip you use is not near as important as the pressure of the grip you use, and trying to keep it semi loose until the "hit"