When I first started this hobby, I used the fueling valves. Robart makes one that is streamlined, that flips up............

Then I went to a third line with a plug.......

After that I now only use two lines, one for the engine fuel supply and one vent. I pull the line prior to the filter and use that as the fill line. Less complicated, however for my fully cowled mustang, It still has the robart filler.