I use three lines. top line is vent. comes out the front, clockwise around the tank and back to the front then through the firewall and out the bottom of the cowling. this is so if your plane is nose down the fuel will not run out the vent and cause a fire or mess. the second port on the tank is a single line out to a fueler. make sure it is gas rated(red). this line has a klunk inside to defuel if you choose to. the third line is klunk to line through the firewall, inline filter and direct to the carb. attached is a pic of the carb and fuel lines. the one is from the tank and the other is on a blind nipple and goes to the fueler. in an emergency I can switch the two carb lines and I am back in business. such as the main ckunk plugging up or filter plugged. fly the rest of the day and go home and fix it.