I would never use a fueling valve they are expensive and redundant as well as on occassion can cause running problems.

My preferred method is exactly as you do with your trainer except you make a brake in the carb line where it is accessable with a short piece of brass tube. That is where you fuel from. I have never found a glow plane yet with an unpumped fuel system that needed any more than a two line system. The exposed part of line supplies an easy place to allow pinch tuning of the engine.

John