Bodyslide/OutfitStudio: how to add new sliders to an outfit in using .osp file?

[Apahguinsimo]

Shot in the dark here, but I'm trying to edit an outfit I've already added a slider to using its .osp slider file so that I can add more sliders. However when I load up the outfit in OutfitStudio using the .osp file, the sliders save in OutfitStudio but do not appear in Bodyslide. If I start over using the original .xml file instead of the already edited .osp that OutfitStudio built, then the sliders show. 

 

How can I make new sliders using an .osp file that actually show up in Bodyslide?