I always try to keep things as simple as possible. I use a third line that is positioned hard against one of the bottom inside corners of the tank. It will empty the tank dry and I don't have an extra clunk vibrating/bouncing around inside of the tank. The end can be a fuel dot or just tucked back into the cowl. I use a catch bottle at the muffler to catch any over flow of fuel when filling.
Sooner or later a valve will give you problems. I have used both the Great Planes and dubro models, the simple robart fueler works good but has to be mounted to the outside of the plane.
Fred