Chas - My first fret job looked something like that ! :blink: I might check these necks out. Their fret theories may prove out OK, and they are aware of string variables, as they recommend certain strings. But I believe if you deviate from their string specs, these necks will also go out of tune.
Willem - Your headstock tuner reminds me of a comment Keith Holland made. He warned of tone changes by increasing the mass on the headstock by using heavier tuning machines. But in an earlier video, he recommended the use of a headstock tuner. So, do you notice a change in tone when a tuner is clamped to your headstock? Thank you for asking technical questions, as I really enjoy the technology of guitar as much as I love the music they make. Sorry to hijack your thread, though.
Bear - I made the same assumption about stretching the string over the fret, but that turns out to be only one of many variables - and not even the most important one. That assumption went out the window pretty fast! I never built a watch, but I built a car before I got my driver's license, and I built a computer shortly after getting my first calculator. And then there's the research i did when I started dating girls!
Stuart (and Bear again) - Another surprise finding for me was that the pitch error was the same whether the capo was right up against the fret or half way between them. Closer to the fret is more damaging to the string and the fret, however. I used to capo close to the fret, but based on what I saw, I'm going to start placing the capo further away. Weighing clean notes, fret damage, string damage, and fretboard damage, this looks like about a quarter inch behind the fret. Stuart, yes, there will be intonation issues up the neck after the capo is installed because intonation is based on the scale length then each string is compensated. With a capo in place, the scale length is shorter, and the compensation is no longer valid. The b string is the worst because it requires the most compensation.
Dave - What Chris said.
Chris - how far from the fret did you place your capo?