OK John, I was typing as you were posting the 2 photos. I thought you were using a tee fitting with one line going outside the cowl for external fueling access. All you show there is the same simple system that every open cowl upright engine trainer uses. Just unplug the carb line at the carb and pump fuel till it comes out the vent line. If the engine is in an enclosed cowl you don't have access to the fuel line unless you loop it outside the cowl somewhere. How do you do this with an enclosed engine??