You can select the VSS prop in the material room and open the material named Template Skin.
Set PM:Gamma to the level you want. It seems to me that higher gamma levels decrease the illusion of depth by lightening the shadowing around the edges of a figure.
Bump can be decreased by decreasing either PM:Bump or the bump level in PoserSurface, or both. I've noticed that some texture sets seem to be more sensitive to bump level than others.

If you want you can save the prop in your VSSProp folder. I've got about ten of them :)

 

PS-- I'm thinking that setting render shading rates below .2 doesn't do any good unless you go through the properties tab for each part of the figure and set the shading rate below the default .2   -- fwiw