Mark, I don't have any CNC tools or use my computer for design, however I have friends that I can get to help whenever I have a need. If you aren't familiar with woodweb, which is a professional site, here is a link to their CNC forum. This is a pretty active site, and I'm sure you'll get an answer from someone who's job is on this subject.
They always encourage new people to use their search in the upper right corner of the page, before asking a "redundant for them" question.
I hope this helps.