Poser figures have many material zones other than SkinHead and SkinBody. You need to apply your new material to each and every material zone in the figure in order to completely replace the drfault ones. The zones have slightly different names in each figure, and how you apply materials to them depends on which version of Poser you are using. Generally you can see the entire list of materials in a drop-list within the material editor of your version of Poser.