Keep in mind that we still aren't sure exactly what the size of the muscle, skin, fat, feathers, and other tissue on top of the skeleton for dinosaurs were. Not too long ago we had to completely re-imagine how edmontosaurus looked after the dinosaur "mummy" Dakota was discovered where we it turns out they had huge muscles on their rear legs resulting in a huge butt and so our speed estimates were far too slow. So all estimates for dinosaur sizes are just that, our best estimates based upon the evidence we have. The more we learn the better we understand how much we don't really know about the Mesozoic Era.
