other issue bill mentioned in re: IDL attenuation bouncing off diffuse surfaces.  IIRC he said to drop IDL value to 0.1 or 0.2.  we know we may get light multiplication in occluded areas if diffuse surface values too high or if IDL value > 1.0, but bill was saying even 0.8 (original value recommended by stefan in first release of IDL (poser 7)) is too high in current version(s).