I recommend you not use that resource I released. It's a lot more broken than I thought it was.
I recommend you get the Oblivion/Skyrim NIF importer for your modeling tool of choice, and use the BodySlide++ for Caliente's Big Bottoms Edition mod.
Then, you import the NIF into 3DSMax (or whatever) and make sure to create the skeleton with dummy nodes (an option the importer provides). You need to relink the bones yourself, but that isn't too difficult. Then you need to do some rescaling to make it fit Source proportions.
That's about it, though. The rest is more standard model-hacking techniques.