It's also possible that they would be made invisible by a MAT Pose which came with the skirt, which just changine the main texture doesn't affect. You would have to pose the figure amnd skirt, adjust the body handles to deal with any poke-through from the legs, apply one of the original textures, and then replace the skirt texture with yours. If that sorts the problem, save all the materials for the skirt as a Poser 6 material collection. These can be converted to a Pose file, it just needs a couple of changes in the first few lines of the file, and the correct filename extension. Unfortunately, there are other ways of making these objects invisible that wouldn't be recorded in this way, but which can be done in a MAT Pose. Compared to the MC6 file, there can be extra sections iin a MAT Pose, making some body parts of the skirt invisible.