We run 3 Downriggers on our 31' Tiara Open and our trailerable 22' Islander. I believe 3 downriggers is the most you need no matter what size boat you have. If I personally had to outfit any boat smaller than 22' I would only go with 2 downriggers and a lot of everything else (Lead Core, Copper, Divers, etc.). I think less downriggers means more bites and action. With 3 downriggers you get a lot less tangles with lines and wires crossed like in years past, as well. We usually run 3 downriggers, around 10 Lead Cores and Copper (surface boards, etc.), and 4 Divers in our "normal" charter spread. The only time I think 5 downriggers would be beneficial is in the harbors in the fall.