Thanks for that - but Vader isn't the same size in the frame in those pics - notice the chest pieces are also smaller on the figure.
Here's a gif made from those two images. The cape is higher on the neck, as we know the chain was over the helmet in this scene. And I'll admit, it does look like the helmet needs a bit more flare out on the bottom, but the size seems okay.
Liked because it's too big.
https://www.sideshowcollectors.com/images/Vader_ss_trans.gif
That is correct Dave. 85% of the reason the helmet looks off to people is tied to how the head itself is mounted to the figure, 10% to do with the slope of the cone part from a profile view, and 5% the length of the flaring part.
The head is a perfect 1/6 scale of Vader to me, so if it seems small, then it's the body that's the issue. When people actually get their Vader figures, they'll see that if you increased the size of the head on this figure you'd have a freaky looking Vader like the old Hasbro where the Head was poorly sized compared to the rest of the figure and other figures in Hasbro's offering.