I caught fish last weekend trolling and never found much concentration wise on the fish. We did catch around 30 fish, and most of the time speed was between .7 & .8...as TB said, it had more to do with how the fish wanted it than the depth I was pulling. And this time of year you have to hit them on the head...water temp was almost 51 where I was fishing. Just a degree or two warmup can make all the difference though. If you can catch the rise in temp from 50 to 53/54, things can get good in a hurry.