I am guessing this was intended to be similar to the thermal control layers worn under space and deepsea diving suits.
Anyways I tried to simulate this using the recon armor helmet. I didn't want to have to carry and equip it as a separate item but instead want it to appear automatically when the PA Helm is removed, so I added it as an Armor Addon. I added this to the form list linked to hair/headband/hat as with the recon helm.
Unfortunately, when it shows up in the game it clips the top of the head and hair as shown: http://i237.photobucket.com/albums/ff292/VonGrantoven/underarmor.jpg
I tried moving the NiTriShape up in Nifskope, moving the Head NiNode, and even duplicating it and scaling it up, but it seems that changes to the nif do not show up in the game! http://i237.photobucket.com/albums/ff292/VonGrantoven/Underarmorhelm.jpg
How can I adjust this to get rid of the clipping?
Any help most appreciated