Thanks for making this its own thread, sorry if it was a pain to move
Not your fault, that was mine. I don't move/merge/split topics often so it's likely more my lack of interaction with modding software than anything.

No worries. I just thought you'd get a better response here since I know Darth Delicious and some other customizers aren't always as active in the collecting portions of the site.
I tried hollowing out the helmet and popping it onto my VOTC Stormie, but it doesn't look right. The helmet goes all the way to the shoulders (making the figure appear to not have a neck). I guess I could try not hollowing it out as much...
That'd be a start, to not hollow so "deep" when dremelling the helmet out. What I'd suggest is do a little at a time, try a fit, do a little more, try a fit, do a little more, try a fit... Better to not have hollowed it ENOUGH than TOO MUCH. Hollowing's like every other bit of customizing though and takes time to get the knack.
I cut my finger hollowing a helmet cast the other day that I went through the surface and right into my thumb as I held the piece... It happens a lot.
If you do the removable helmet (with a dude's head underneath), I don't THINK you can hollow the CCP head so it's able to just snap on the Stormie. You'd either have to change the neckpeg on the Stormie, remove it and attach the CCP, or just make a straight cut for both and glue the CCP on if you wanted (no articulation then though, at all).
It's more work in a way but if you want the removable helmet and don't have another stormie helmet to try that with... It's maybe your only option.