This was the issue with the tanks in the L39's. On approach, fuel would rush to the front of the tank, starving the engine, and inducing a flameout on finals (not the best situ!) I cannot advise about tubing etc.... but many solved the problem by using tanks that keep the fuel deep and in the grasp of the clunk. I presume a UAT/header type tank would also solve the problem. Do you have room for a header tank? how's things progressing with your A4?
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(more experienced people, please correct me if the above is wrong)