I noticed a few small other details which are missing, maybe you already planned to do them, but I will mention them anyway.
Photo from left to right:
1. The triangular shapes under the nose I talked about earlier are a bit recessed, and I found a photo. Hopefully it is clearer now?
2. There is a small line (see arrow) on the left side of the skull which isn't on the right side.
3. The jawpistons are positioned in a hole in the jaw which are angled down a bit.
4. In the nose are two small holes (photo is from the M1 skull but there are also there on the T1 skull used in the movie).
View attachment 503187
2: Vice versa actually