Quote - I and others who kindly volunteered have tried and failed to convert some of my frequently-used procedural shaders for GC.  I need very specific effects, which may not be possible for some reason using Poser shaders when GC is enabled.  I don't know enough about the matter to try to approach it with mathematical precision, so I have to eyeball it.  That hasn't worked.  As a consequence, I just can't make the jump to GC.

That explains it right there. When you're moving your render towards physical modeling with using IDL and inverse square attenuation, but then skip gamma correction, that is the conversion from linear to screen color space, then it is no surprise that the results don't turn out as intended.