UV Mapping is based on faces normals. If you got two different transparency maps, only one can be rendered at the same time, dependending on the viewing angle. You can't see the inside and the outside at the same time. For this, you need to make two different cylinders... You can have two different textures but Poser can't do it. For this, you need a software that can handle some kind of... layers. For what I read, Poser 5 will be able to do this. A normal is a vector which gives an information about which side ( outside-inside ) can be seen. So the inner side can't be seen from an outside view because it doesn't exist for the renderer... Not sure if I understood the question :)