you could also rig a spoon on an 8'-10' leader with a snapswivel and clip it on the line already set. the rig will slide down to the belly of the line and troll at about half the depth of the set. on lake erie we used to call it a "slider"

it gets real interesting when you have planer boards out either side with 2 rods on each, 2 downriggers down with a set and a stacker(each with a slider) and 2 rods flatlining with lead or a dipsydiver. for a total of 14 baits on troll