i think face_off has a tutorial on his website about how to add extra figures in the Real Skin Shader script so as to accommodate more figures. 

http://www.users.on.net/~pkinnane/RealSkinShaderSupport.html

And, if I'm not mistaken, there was an update some time after V4's release to incorporate v4's material settings into the script (update date 05/26/08). Just checked, and indeed V4 is supported, so M4 is supported as well since they share the same surface names.