The longer the puzzle persists the more we PPRuNers learn about airliner fuel systems and many interesting associated sub systems.
Pity we are not getting some inputs from the two pilots and Boeing who seem to be all overcome with secrecy. No doubt the investigation board sifts through this thread for ideas and what ifs.
Another thread has just addressed the complexity of the Joint Strike Fighter fuel system which has been subject to successful? exhaustive ground testing. As a TP I hope I can get access to the items which are planned for flight testing. It is likely that fuel will be used as a convenient cooling medium and there may be a problem with heated fuel which has elevated vapour pressures. The FADEC, FBW and software will need to be 'state of the art'.