My problem was never the size of the helmet.
I posted this on Statue Forum, and I'll post it here just so SS is more likely to see it.
OK, there is a GREAT thread on the RPF that discusses just what is wrong with the helmet.
https://www.rpf.invisionzone.com/index.php?showtopic=101885
Here is a great photo comparison of the 2. Credit goes to phase pistol on the RPF for the grab:
Problems that I see.
1. Look at the bridge of his nose. It should be painted silver, plus the bridge should be MUCH wider.
2. There is no widow's peak. The ANH Vader is famous as the only incarnation to have this peak. Why did they leave it out?
3. The right tusk (left on our side) should be black or at least slightly black as in this Tantive IV photo.
4. The grill under the chin is too far recessed, that area of the neck is angled in too far.
5. The cheeks are just flat out wrong. I see exactly what is wrong with them, but it's very difficult for me to put into words. The distance between the lenses and the ridge on the cheeks is too short, the "frown lines" don't look wide enough, and the cheeks themselves are not wide enough.
6. The mask/helmet is too symmetrical. This is supposed to be ANH Vader, not ROTS Vader.
That unproduced Marmit Vader in the RPF thread looks MUCH more accurate to me.
That helmet looks AWESOME compared to the SS version. Note the black tusk, the widow's peak, etc. and that is for a less expensive figure. I'll still get my SS Vader, but it looks like he may go up on Ebay at this rate. It looks more like ROTS Vader than ANH Vader, IMO.