We know that the old upright awkward tail dragging posture is outdated and biomechanically inconvenient. But what about a partially upright posture, (like say ten degrees)? I mean, T. rex was 40 feet long and weighed 6 metric tonnes. It was like 13 feet tall at the hips, and from what I could gather, its head had a dorsoventral height of 3 feet and 8 inches (so almost 4 feet, if you account for a bit of neck length too). Let's say if it carried itself with a slightly raised throax, around ten-ish degrees. For an animal of that size, that would be enough to carry its head fully above hip level. Add an additional 6 inches of height from skin and cartilage, it would have a total head height of 17-18 feet (I think that's where the JP Rex's measurement comes from)
(My best attempts at visualizing it)
On the other hand, it could have also angled its body downwards, which would lower its height, in which it case it would look something like this
(Credit to Paleonerd01)
I couldn't find much on the web on this particular topic until I came across this
The comments section's full of well established paleontologists talking about this issue. The consensus seems to be that ten...maybe twenty degrees is possible, but not something you can really confirm either way.
