Are you sure that you didn't make an error following the kit's instructions? I just used a copy of Silverstag v0.27.3 and installed the kit you linked on top of it with everything working out fine. Rolf is a bit lighter in skin tone and Nizar looks changed a bit, but those appear to be intentional while every other male looks roughly as they did in native. The women are another matter with the same basic look.
So that would be my recommendation. Make sure you didn't forget to change one of the load_resource lines to load_mod_resource, that each of the resource (.brf) files is in the resource folder, that all of the textures (.dds) made it into the textures folder and the skins.txt file made it into the main "Silverstag" folder. Overwrite any duplicate files when copying.