That said you would think in these days of technology we would have a system fitted on the a/c which displays (accurately) the actual weight (sorry mass!) and C.G. position.
When I flew the B707-336 freighter in the 1970s we had a system called STAN (cannot remember exactly what the acronym stood for - maybe Sum Total And....) which we used as a gross error check on the loadsheet. I seem to recall it was quite good when it worked. Surely by now the boffins could come up with a system to suit our times!