I think GF files are created when you convert a .mod model to the .x format with Taldren's ReCacher tools. If you want to edit hardpoints and the model, open the model up in CV (version 0.7.5, not 0.8), goto the hardpoint editor and save the hardpoints to disk. Then, edit the model in Milkshape, save it back out, open the model up in CV, and re-import the hardpoints from the file you saved.