I have read about setting witness points to improve intonation, all around strong vibration, etc.
My personal advice, after personal experimentation, is: not only do not bother, but it can actually be harmful.
With roundwounds, strings are probably flexible enough not to benefit at all. Or not enough to make a difference. Fact is, I have neither heard nor felt any discernible difference.
With flats, it can actually break them, especially the stiffer ones. I did it to a set of LaBella DTFs, and the result was that the E string especially went from bright (it's a new flat after all) yet precise to sounding like a wet noodle after doing it. Significantly darker, actually *worse* intonation, *worse* attack and sustain. While setting witness points, you could actually feel the string "creak" a bit. I obviously only set the witness points using my bare hands and some moderate pressure. Now an expensive set of strings is unusable.
Anyway, don't do it.
My personal advice, after personal experimentation, is: not only do not bother, but it can actually be harmful.
With roundwounds, strings are probably flexible enough not to benefit at all. Or not enough to make a difference. Fact is, I have neither heard nor felt any discernible difference.
With flats, it can actually break them, especially the stiffer ones. I did it to a set of LaBella DTFs, and the result was that the E string especially went from bright (it's a new flat after all) yet precise to sounding like a wet noodle after doing it. Significantly darker, actually *worse* intonation, *worse* attack and sustain. While setting witness points, you could actually feel the string "creak" a bit. I obviously only set the witness points using my bare hands and some moderate pressure. Now an expensive set of strings is unusable.
Anyway, don't do it.