We have some skin impressions of T-rex which show that at least some parts of it's body was scaly. How much was covered in scales and how much was covered in feathers is debated. I have seen modern reconstructions of t rex with feathered tails and without feathered tails. I decided to go without feathers on the tail…
That is the strangest reason why a T-Rex would be surprised. I would think something more along the lines of seeing an asteroid coming at him or a volcano going off in the distance. With respect to the work, its coming along well, perhaps post a few references as well.