Well a few days ago I got a stormtrooper helmet in the mail from CHEWIE, which is the mini-bust Gentle Giant variety, a perfect fit for our 3.75" Hasbro figures. I immediately made a mold and made a bunch of casts from Alumilite white plastic. I cleaned them up and painted 2 of them.
Any white spots you see in the black paint on the left eyes of antennae are light reflections.

Here are 2 painted and 2 unpainted casts:

Hasbro's on the left, mine on the right:

And for sandie Hasbro's on the right, mine on the left:

Victory!! At long last, stormtroopers that actually look how they are supposed to! Look how smashed and out of proportion Hasbro's helmets look next to proper sculpts. Holy cow.
Sooooo guess I have about 100 more to paint. I have hated every stormie helmet since 1995, a real albatross to this hobby IMO. The iconic stormtrooper, always a dud.
But now, fixed!!
Thanks again to CHEWIE for his help. I owe you one.