Once the water passes ~58-60°F and walleye scatter off the tight reef tops, flatlining two rods straight off the back stops being enough. An in-line board clips onto your line and planes out to the side, so you can run several lines without tangling and sweep a 60-90 ft wide swath instead of a single track. This is how you cover water and find the scattered pods. Start with one board per side on top of your two flatlines, and add more only once handling them solo feels routine.