Forget the after market pumps and all this stuff with this engine.

I had the same problem with my Ft-160 placed on a GP super stearman. Just use a clamp on the fuel tubing when your tank is full and engine not operating.

Durring operation there is absolutely no leakage. In my case there is no leak even when the engine if off pressumed that I have the throttle fully closed.

Stelios