Femur dimensions estimates, when it comes to extrapolating to phylogenetically and morphologically disparate organisms are inherently inferior to volumetric ones, of course, a volumetric estimate is only as good as the model used and Greg Paul's are inaccurate, this are his skeletals of Stan and Sue, compare them to the ortographic images of the scanned skeletons from Hutchinson et al. study available here and Scott Hartman's skeletals. You find considerable scaling mistakes and conscious choices at articulated the bones that betray Paul's biases to making them as skinny as possible, like the scapular blade being too high in the torso or the concave gastralia that Hutchinson et al. already mentioned as inaccurate in their comments. Using a more accurate reconstruction and following a similar method to Greg Paul, Scott Hartman has estimated the mass of Sue at 8.4 metric tonnes. Now, for the article, since there's no paper that explicitly calls out the 6 tonne estimates as improbably light for the largest individuals I don't feel like we can outright replace it, maybe put up a range?