Just a bland question: what sort of system and which renderer are you throwing these massive files at? Can Poser really take advantage of that level of detail?
I mean, when you consider how much painting (clone/smudge/pixelate/other CSx artifice) is done to a texture when creating it from resource kit, and considering the fact that the final products all seem to have burnt-in specular that are going to be a bit wonky with scene lights as well as other issues... just can't see the justification for such high-resolution images.

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks