Everything gets put through Netfabb prior to printing, so there's an opportunity to check measurements, but it'd be far preferable to make sure it's right first time. What I've been doing is to create a primitive (e.g. cylinder for a ring cutout) and using that, but it'd be nice to see a workflow that was based around sculpting jewellery. One thing I use in Rhino is gems with associated cutters - both get scaled the same, both get the same alignment. I think that would mean they need to be on different layers in 3D Coat, but I've yet to find a way to link transform operations to both of them (or work out if they ought to be primitives instead). That said, I'm still adapting to moving between voxel & surface modes.
I'll have another look at retopo, thank you.