okay, that puts some possibilities out of the way.

re-reading your posts to grasp the situation in full detail, I must admit that I've no info on the hair itself, it's all on the skullcap only. Is light-emiitor for the hair itself on or off? An what about the head (since the cap is made to vanish in some way or another).

I also must admit that I've lost track of the skullcap settings. Do I understand correctly that splotches occur and shadowing improves when the cap is visible and fully transparent and light-emitter off, and that the splotches are minimal under IDL when its visible and fully transparant and uses all the face material settings and light-emitter on? It's mainly the combi of fully transparent AND using all face settings which wonders me. How can material settings (especially: any content in Diffuse / Alt_Diffuse) make a difference when it's fully transparent?

Time for some (Mat Room & Properties) screenshots, I'm afraid.
Interesting anyway, thanks for the puzzle :-)

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