Whenever I see a mesh with "upside down" UV I have to wonder has that mesh been mirrored, as only an idiot would UV it that way. By mirrored I mean built and UV'd in a program that uses the vertical Z axis.

Not only does swapping Z to Y axis mirror a mesh it also flips the normals, been so long that I can't remember if Poser shows backfaces or not, by default DS has backface lighting on, so it doesn't show them. This is one of the issues most have no idea about, not only are they working with a mesh that's been mirrored, but it's usually inside out.

In DS hit F2 or go Edit > Preferences, click on the Interface tab and just past halfway down you'll see a label "Backface Lighting" set the button next to it to OFF, click Apply then Accept to lock that setting.

If the mesh is now black in the viewport then you know the mesh is inside out and has been mirrored either top to bottom or left to right. Chances are that a check of the surface settings in the PP2 would show the U and V scale set to -1, which would show they knew something was wrong but was clueless to what it was.

You can do the same "trick" in DS using tiling, so no point making custom UV for it, especially as Poser can't use it.