usafloadc17,
I understand your frustration at this point, but as I said before, I have this same exact plane. There is not issues with the location of the fuel tank, and I've got countless hours of flight on this plane with no issues whatsoever. Reconfiguring the airframe to accomodate a header tank is simply making more work for yourself before you have explored all of the problems. First of all, you don't need the plane to stay at an idle for more than a minute. It's next to impossble to have the plane in a nose down situation without hitting the ground first. Second, look at the situation you are describing. If this happens at ONLY a certain level in the fuel tank then there is something wrong in the tank. If it was because of fuel flowing to the front of the tank and leaving the clunk exposed it would happen at other fuel levels as well. My gut instinct there is to tell you to replace all of you fuel lines, both inside and outside of the fuel tank. I've got a sneaking suspicion that you have a pinhole in your fuel intake line inside the tank, and then then the tank is down below that level it starts sucking air. Pinholes can sometimes be next to impossible to see, so it's easier to just replace all of your fuel tubing.

Ken