Sorry this is so generic - I didn't have a lot of time to put in it.
It would be a solid straight axle, not twin-beam independent. I would love to have independent but my plans are much to narrow for that; and the camber curve would be crazy - just as you mentioned. I owned some Ford twin I beam trucks before, and am aware of that style. For how I plan to use this project, I don't think it would be worth the extra engineering hassle to do that, even if the geometry was decent.
I just did a simple tube shape for the axle in the model, because of the time issue; but I am really thinking more along the lines of a fabricated axle. I was thinking about making it look like an I-beam with the vertical piece cut from 1/2-inch plate and the top and bottom horizontal pieces cut from 1/4-inch - all welded together. If the budget allows, I can have the 1/2-inch piece cut on a water jet with lightening holes...
Hope this helps make the idea a little clearer.