I use a 3 line system for my Cub, and it works fine. I've never used the valves because I've heard the same comments- that they are prone to leakage. They are a really tidy way to set up your plane, but planes tend to get untidy fast when the engines won't run reliably. The other advantage of using a dot is that if you lose your dot (you will), you can just stab a screw in there and keep on flying!