I would do as missileman stated and just replace the tank stopper with a new one and make it a two line set up. Make the pressure, muffler, line go to the top of the tank from inside the tank by bending the tube line up untill it is just below touching the top of the tank and then put a clunk on the second line, like stated the line that goes to the carb, making sure it does not touch the rear of the tank and does move around free inside the tank. Now all you have to do is remove the line from your carb to fuel/unfuel. One less fuel line to worry about leaking air latter on that way.
You can just remove the pressure line when fulling and when fuel comes out that line it is full and nothing will enter the muffler.