Could be the blind leading the blind! LOL
What my eye is although picking up more and more is where the mean falls. If price spends a good amount of time at where the mean falls given the way the upper and lower channel lines are drawn, I feel as if the channel is legitimate.
Furthermore, I think Db also said once that price tends to move around the mean in equal amounts, and I see this here too. When price goes a bit one way above the channel, it goes the same amount in the opposite direction. When it ventures out further, it also does so in equal amounts to the other side. There is a certain kind of symmetry that I sometimes see to means.
It is I think the mean that is more important than the extremes, so when we draw in the initial channel line and then do a parallel to the opposite side, if the mean does in fact capture where much of price trades then I think the channel is drawn well.
I hope I'm not out to lunch on this.