most, not all of my planes have a 3 line set up a fill line, a pressure line hooked up to the muffler, and a fuel supply connected to the carb.
when fueling disconnect the pressure line for overflow and fill through the fill line, extra fuel can be captured in a small container and poured back into your fuel can. on a couple of my planes I use a small machine head cap screw for a plug on the fill line 1/2" is long enough push in and screw out. for my cowled models I use a fuel dot they work great also.