Sidney LoRez with polygon smoothing in Poser 7 (click to enlarge)

The head was reduced in Wings3D by selecting and deleting vertices manually.

The body was reduced with Polytrans. Polytrans first triangulates the mesh, then reduces it. Then the mesh was re-quadrangulated in Wings. Polytrans uses an automated reduction algorythm, so the resulting mesh is non-symmetrical.

The only way to keep her body strictly symmetrical would be to reduce it the same way as the head, by manually selecting and deleting vertices in Wings.
But  because of the expression morphs symmetry for the head is a lot more important than it is for the body IMO.

Sidney LoRez is more intended for clothed characters or cloth creation, not as a standalone to develop bodymorphs for, so I reduced her body as much as possible while still looking good with polygon smoothing enabled.

If I need more body detail, I can use a medium rez version which combines the new reduced resolution head with the standard  resolution body, resulting in a mesh that is 57000 vertices heavy.