I always found salmon to like structure i.e. log jam back eddies with brush hanging in the water just off the heavy current. In the early light fish can move into the bottom end of the drift and since they just swam up a break maybe alittle pissed off that some foreign object is right in front of them so they bite ... sometimes.... To help you answer your tailout speed, the water traveling it's path of least resisants piles up before it hits the shallower water of the break sometimes you can't see it from the surface but it's happening this is the sweet spot and fish will rest here before moving up in the hole. Then again maybe not I hope this makes sense for you