Rollo, I've built two five-string necks so far, the first to go with a wooden head pot I built, the second to convert a tenor to 5-string like you are doing. If I can be of any help, contact me through personal message. Also go to this site: The Musical Instrument Maker's Forum for help. If you register you can access their library of expired discussions, also get free software (some of which I contributed) to help you do the fret spacing.