When you say "right side", do you then mean the left on the picture? Just to be sure I got it right.
...the left is perfect as far as I can see, the right comes out just a bit in the rear making it look wider overall but the face is right on in terms of proportions to the helmet...that's why depending on how you rotate it, the neck will look wider or narrower compared to screen shots. Here's a very old comparison I did showing how the neck can look different but also that it's not as narrow as the ESB movie poster helmet or 20th Century ESB. The neck differences were at one point assumed (by myself) to reflect two different helmets but that turned out not to be the case. Others here had speculated that there was more than one original sculpture, something I was never convinced of. 
