Due to the complexity of modelling the infinite number of variables, we may never get a final answer.
Nah, they WILL get there.
The
fuel: they have big samples of it - can test as much as they need to.
The
environment: they have air temp data from the whole BA38 flight and previous flights if necessary.
The
fuel system: they have the real one to test with, plus lots of copies.
They will fly test flights if necessary (remember the ATR72 icing investigation), and they will keep plugging away until they get there. They won't give up on one this important.