the shape you have is way to "blocky". i used to work for Deering Banjos and have much experience with designing banjos in Mastercam. you can only use solids to a point, then you must use surfaces to trim the solid to or just create the surfaces needed. for good surfaces, you need good wireframe.
take a look a the pic below. every different color is a different surface. the edge curves needed are the perimeter fro each patch. then use the chook coons the generate the surface.