Hi Jamie,
That was quick ! Now I see what you're doing, and it looks great. I think I can help you. Keep in mind, that my full hub was reverse-engineered essentially over the phone, and email. Guaranteed there are shape errors, but you'd have to be a total expert to find them. It was a guy named Keith Hironaka that gave me basic dimensions. You will likely have to tweak the shape here and there.
So, you need the rear half of the barrel ? I don't need to charge you money, but I would like a few pictures when you're done, and I'd also like you to never share the file that you print from. It took me hours or days to model. I have the file in SpaceClaim 3D CAD software, so I can export as a high resolution stl file for printing. The file might end up being large, so maybe we'll need an online file transfer system.
Do you have the barrel supports ? There are 4. I assume you are not using a prop spider ?
Tom.