So now I'm working on different CAD/CAM options. The one that seems the most promising (but not the cheapest) is Rhinoceros and CamBam. Through educational discounts I can get Rhino for $195, but it's still a good chunk of change. CamBam and $149 isn't cheap either. As a software guy, I know I don't want to reimplement Rhino, but for the feature set I need, CamBam might not be necessary. Other options are PyCAM and HeeksCAM on the free end.
To help make things clearer, I've been using Rhino in eval mode to develop 3D models of objects, and then exporting the profile information for use in the CAM systems. With CamBam, I find that unless I want to do a simple 3D profile, I end up redrawing some of the features (for example, to build a pocket or for a 2D profile). I suspect this is just my lack of experience. I'm spending most of my time in Rhino, since I'm pretty much sold on using it for CAD.
Next I'm in the process of designing the solid body banjo and a neck. I have the body layout I want, and no I'm working on the neck heel profile that I want to fit it. I'm going to spend some more time with CamBam to see if there are clever ways to have it only do a profile cutout along the edge of the body, since the top surface is completely flat. Using a 3D profile requires a lot of traverses that are incredibly inefficient. I expect there's a way to do it.