A while back Mason also suggested using the blender node with a small transmap to apply the tanlines by using a bikini to make the transmap. Would only work for Poser 5 but it would work. I have a tutorial in the Poser 5 Secrets to create the transmaps for makeup and how to apply it tothe blender node. Try it if you're using P5 and you won't have to create a seperate texture map.