I should share this, because much of it was shared with me- and it has helped me enormously. I've been building these things for less than a year, and I now find that each new instrument I finish plays like a real guitar. For the love of Gitty, some of them may even be saleable... Anyway, here goes.
I was initially shy of showing my builds to my friend S. Not only is she a skilled carpenter and fully qualified boatbuilder, she does not suffer fools gladly either. But she was really taken with RtB#3 (24"scale, fretless, acoustic, Partagas No.6 box), and offered the following tips over the ensuing weeks:-
* Consider your box. Is the top thicker than the base? Maybe you should turn it over...
* (This may not apply to US builders with inexhaustible supplies of poplar necks, but...) Why are you trying to make a hardwood neck fit a softwood box? Why not actually build your own boxes to fit the hardwood neck options that you have?
* Trust your woodworking skills, and work on them. Example- I asked her to build a mitre box to make the accurate, parallel, cutting of fret slots easier. No, she said. Make a good, accurate score with a Stanley knife (do you have those in the US? Ubiquitous craft knife), then ease your fret slotting saw into the score and saw away. You will become better with practice, she said. Do you know what? I think I have.
* Keep it simple. Personally, I'm not convinced by this one, because there are some real beauties out there in the CBN- but then I wonder, do they all play like RtB#13 does. Oh Lordy...
* Here's one I worked out for myself. I had intonation issues- until I realised that cutting an accurate slot for a zero-th fret was INFINITELY easier than planting a nut dead square. Let the all-G 'chord' sing out, brother!
In summary- I guess that 95% of the above is already known to 95% of you. If, however, just one little piece of advice above helps someone to build a better CBG, the I have Passed It On. No more need be said.