You might want to read the "Opinions on Boucher Minstrel Design" topic. I'll eventually have a full size downloadable plan on my website, but It's not ready for primetime yet. There is a preliminary front view and additional details in my photos section._
You might want to check the banjo sightings database.
If you click on the more info button you can get the dimensions of various parts of a number of the banjos.
thanks Randy Now I can make my patterns.