I had this problem as well. If the sliders in bodyslide (Low weight and high weight) match, the body shows up fine. Only the high weight sliders effect the preview and you can use the arrows at the bottom to make both sets match. My problem is the outfits don't change. When I look at the .nif files, they look right, but they don't display properly. This seems to be outfits that include a CBBE body. The .nifs look fine, but the outfit doesn't.