I think that they work well at all speeds. I'm sure that performace would be better at higher speeds, but I get all I need at low speeds. This past weekend is a good example. Fished a tournament and had to run 27 miles into a large swell (3-5') dead on. I set the speed at 20 knots and only used the QLs. Did not trim with the motors. I could have run faster but had a group of kids and we did not take a beating. The old seacraft came through.
33.6#, 4th place finish.
BA