Actually I always use a fuel tee in the line from clunk to carb for filling and draining the tank. Keeps it simple and you don't have to worry about fuel being pushed into the carb the gas carbs have a needle and seat that close so you can pump in the fuel but it only goes to the tank. I have done this way for years and most of all the guys I fly with do the same on gas. Oh and like what was said no line to the muffler just vent it to the bottom of the plane.