I'd say install them in the directories where they are meant to be and change the model path in clandoc000.txt. You can find clandoc in /antitribu/vdata/system. In clandoc, look for "Player_Clanname and then search for the model paths.
I don't have antitribu installed so I can't be certain, but I think you should look for the vanilla clan names.
In any case, make certain you install the model/skin files in /antitribu/..., not /vampire/...
Changing paths for the skin files is not a good idea because the paths are set in the model file. there are tools to change that, but keeping the original path and changing clandoc accordingly is usually the easier way.