Allen, Ever since I first tried it around 1980, I have used nothing except Prather products fuel tubing for all of my fuel lines. It was not available for a while but a quick search finds it in stock at several hobby shops. For .15 all the way to .60 and bigger, the Medium tubing works well, it's a pinkish/red color. I plumb inside the tank with it and also the fuel line to the engine. For a vent or pressure line, I use blue tubing so that my lines are color coded. I liked the blue Aerotrend but it's long gone, my latest roll is Venom I believe. I like and use Kraft tanks whenever possible but I am not a fan of the black tubing that comes with them, it didn't last very long for me. My experience with the Prather tubing shows it lasting many years. If it does not seem flexible enough for you, replace the middle portion of tubing inside the tank with 1/8" brass tubing. You will end up with brass tubing through the tank stopper, a short piece of Prather line, a couple of inches of brass tubing, another piece of Prather line and finally, the clunk. That configuration will always flop to the appropriate side of the tank but will not let the clunk go to the front of the tank if you have an abrupt stop ( I have had that happen and it will have you scratching your head). The brass tubing submersed in fuel will probably deteriorate faster than the Prather tubing so keep an eye on it or replace every few years.