Of course, Ken - all fair comment. You mention the bar: we both use Basil's high-density plastic bar, and we've both noticed the effect it has on tone. But let's not lose sight of the fact that you can *expect* it to affect the tone, because it's directly a part of the interaction with the string and its vibration, in a way that a 3D printed puller is not.
You comment on the best tone coming from guitars with round shafts. You attribute that to "maximum contact between cross-shaft and puller". Actually, that can't be so, from a simple geometric (engineering) standpoint. If you consider the nature of the contact between a round shaft and a puller with a round hole in it, there can only be contact between them at one point on the periphery. Well, let's not forget the screw as well.
With a square cross-shaft, I would argue that there is a much greater area of engagement between puller and cross-shaft. For a start there is a tighter fit, and then there is the double rectangular area of contact to consider. I'd say I'm sure your ears are giving you the right message, but that we need to look elsewhere for why the tone is as good as it is.
As I say, a bit off topic, but if time allows I have a promise from my 3D man to print me some trial pullers.... It would be fun to try them. The acid test would be "can you hear a difference without looking underneath?" I think.


