I refuse to use a fueling valve. 75% of the plumbing problems encountered at my field can be traced back to a fueling valve. It doesn't matter which brand. I use a three line system. The third line is used for fueling. It can be run out the bottom of the cowling or into a cute fitting that holds it on the side of the cowling. A plug, or "dot" as they have come to be called, is put in the end of the line for running, and removed for fueling. It's very reliable and cheap. If the plug falls out (exceptionally unlikely) the engine will still run without muffler pressure. If you want to un-fuel with the same line, you need to bend the brass tank tube down so that all or most of the fuel can be sucked out.

IMHO