I have a Dura Plane (brick) that has the same problem.I removed the tank and replaced the clunk line(looks just like the drawing earlier in this post) but when the plane is nose dow,it sucks air and makes the plane die.I can see it when I hold the plane,and tip the front end down,it idles right down and will stall unless I tip it back level or upright in the front. I am so used to dead stick landings its not funny,maybe 1 out of 12 time I can keep it running. What about a small header tank? I also have a Hanger 9 tribute I am leary of flying because I'm afraid it will dead stick and not being used to it might crash.I am running a 40LA engine.I know what you are going through!!!!!