What engine are you using? Use LARGE brass tubing for the tank and LARGE fuel line for the pickup. Clunk line goes to fuel inlet at the carb, the other line (vent) gets run out to the bottom of the plane and left open. DO NOT use mffler pressure on the tank! This creates the possibility for explosion or fire. You can use the third line for fueling if you like, just remember to plug it after fueling.