I'm refurbishing my KF IV after ten years of sleep. It looks like the header tank is half full of very old nasty fuel. I see the lowest point in the fuel system is under the seat, but there is no fuel sump drain. Seems to me this would be the perfect place to sump the fuel, and be able to drain the whole system. I don't think I want to try and drain the tank in the fuselage. I may have to unhook the fuel line at the engine and tip the old girl on her nose. Or better yet, hook up an electric fuel pump....