Why not just make your tank A three line, two klunks + pressuer??? Then either make your own or buy A fuel dot for the fill drain line.
I don't like to over think things. Years ago I had my way cool filler valve stick and end that days flying with that plane. French is right, stay away from those things. Never seen one not go bad over time.
A three line is just A normal set up with the third line set up just like the main line to the carb with A clunk so it stays down when you drain the tank. The outside of this line pulls out of the dot for filling and draining.
On A cowled plane I always like to use A small piece of fuel line slid over the lines to the pressure and carb lines as keepers and I never remove these two lines or clamp them to stop the fuel flow. Nothing like holes in your lines to slow you down.
A three line tank just works and I don't have to think about it. That thinking stuff hurts!!