Thanks for this thread - I've run into the exact same situation and have been researching the 3 line vs 2 line filling design for a week or so - glad you folks put up the schematics as they are very helpful. I built my tank as a 3 line system thinking I'd have trouble disconnecting the line from the carb inside the cowl, but then got the GP Easy Fueler Valve which makes it a clean installation for a 2 line system. Any suggestions on what I should use to seal my open 3rd line? Is epoxy a possibility or does the fuel act like alcohol and loosen it up?