I agree with Pe on this. I used to use two clunks in a three line set up, but have since eliminated the "fill-empty" clunk and line. It's just not needed. Just leave the nipple on the fill-empty line inside the tank short, and don't attach a fuel line and clunk. You only need to tip the plane to the nose to completely defuel, and never a worry about tangled clunks inside the tank.