I appreciate that salmon are different, I just practice moving to the top regardless. Never gave it much thought, and never had a problem. I agree with the earlier statement that there is no magic rock. With the numbers salmon moving through a pool at a given time it is usually more a matter of finding what they want rather then being in the right spot. If someone slides down into my spot when I am off playing a fish so be it. If I catch a fish they missed great, and if they hook into one then the spot opens up again and I can slide down if I want.
This is of course on smaller streams such as the Vedder. On the Fraser your rod holder marks you spot.