The key to success with the UAT is not just total saturation but total and complete PURGING. Dont do this with the engine running (potentially hazardous, time wasting, and uneccessary) do it by using the engine fuel pump with the engine fuel line diverted to a fuel container to receive the diverted fuel. Then, with the model orientated so that the UAT is VERTICAL, delivery line uppermost, (or just by holding the UAT vertical) run the pump via the GSU prime mode (or just connect a battery direct to the pump) until clear totally bubble fuel -free comes out of the fuel line even when the model (ie UAT) is shaken quite violently. Then connect the fuel line to the engine and fly and you will not have a problem regardless of tank orientation. REPEAT the procedure if you drain the UAT.
Regards,
David Gladwin.