Out of interest what would be the max fuel imbalance allowed and still maintain controlability, when running both engines from the same tank?
From the 777 Flight Crew Training Manual:
"The primary purpose of fuel balance limitations on Boeing aircraft is for structural life of the airframe and not for controllability limitations."
"Lateral control is not significantly affected when operating with fuel beyond normal balance limits."
"The primary purpose for fuel balance alerts are to inform the crew that imbalances beyond the current state may result in increased trim drag and higher fuel consumption."