louw is certainly right abut flying for years withour pressure lines to the tank. When control line was all the vogue centrifugal force provided the pressure via a wedge shaped tank. With all that in mind we have progressed to the point where a pressure line is essential. The three line system works well if you don't forget to plug the filler line but in most cases two lines are fine. If you have trouble disconnecting the line at the carburetor get a fuel dot and fill from outside the cowl. They work realy well but you should remember that they have fuel under pressure and will spit at you if you misuse them.