The 744F has a built-in weight and balance computer that takes data from a sort of strain-gage scale on the five gear struts to come up with CG and weight. The system is very accurate. Of course, the company dispatcher figures this all out on a computer and you are handed a weight and balance sheet before you depart. One checks the two values to make sure they seem reasonable. It was company practice to use the dispatch numbers. I once had a 17 tonne (38,000 lb.) disagreement which came from a bad scale reading 450 kilos low on 34 pallets. The plane was smart! BTW, as I recall, 17 tonnes was only about 3 or 4 knots difference in the takeoff numbers, although the fuel burn would have been off on a long flight. Great airplane, we could upload about 250,000 lbs of payload across the Pacific.