While I appreciate your tenacity, this just isn’t something you discover from reading a book.
No of course not, which is why experiments are performed and data is collected on the matter, which is
then stuck in a book. Like you how you just summed up your experience in a post. Perhaps you meant that you think whatever stuff in books of compiled data contradicts your experience, and in that sense the books aren't useful for learning?
I’ve owned well over a hundred bolt on guitars—I know how they should sustain and, alternatively, ring when played acoustically. In my experience you can usually tell whether a guitar is a good one by playing it unplugged. A good piece of wood will vibrate—I can literally feel it in my balls when I strum a chord (I wear the guitar low lol).
Leaving aside questions of the validity of the data set, whether it's free of biases like overestimating occurrences of something or perceptual distortions and just taking it at face value, it doesn't have to be the quality of the wood causing that. An explanation that may be more in line with the physics could be that if you don't feel the guitar vibrate, it's because too much vibrational energy (in the frequency bands we can feel) is lost to a non-ideal neck joint changing how the neck absorbs energy, bridge configuration, etc. If you can feel the guitar vibrate, it's because less energy is getting sapped by sources like these and so the fraction that gets lost to body vibrations is larger, enough for you to feel it.
I'm not trying to say you didn't notice some correlations between things, or felt the body vibrate, or heard differences. Those are interesting and valuable bits of information that, like you said, (initially) comes from experience with the physical systems themselves. What I
am saying is that it appears that physicists have heard these differences and noticed these trends too, and taken the time to investigate through experiments and such and pin down
why these phenomena happen, and the measured data strongly points to it
not being the body wood causing it but other factors.
Yes, a couple times I went through the hassle of trying a different neck on the rejected bodies—no improvement. So yeah I sell them and cut my losses.
This is an interesting observation for sure, and reminds me of some of the work I've seen related to dead spots. Apparently it's possible to have dead spots that seem like they follow a body even though dead spots are caused by the neck absorbing sound energy at the dead note's frequency. My guess is that it's gonna be something to do with how the neck is mated to the body, but like I said I need to read deeper into that area of literature to see what's been tested.
I’m not dealing with used necks and bodies here—these are CNC cut brand new pieces that fit perfectly. If they didn’t I wouldn’t accept them.
Of course, but what's the tolerance on "perfect"? You said you're using Warmoth parts right? A quick snoop through the (un)official forums turns up people saying that they have neck pockets accurate to the spec'd dimensions to ±3 thousandths of an inch. I didn't see any flatness measurements, but if we assume something similar for the evenness of the bottom of the pocket then we could get up to about ±0.66mm of deviation up or down at the tip of the head stock, and around ±0.16mm of deviation in saddle height at the bridge for a given action height. Assuming I did the trigonometry mental math right, of course; I haven't diagrammed that out yet. This is assuming 6 in from heel to bridge, 24in from heel to tip of headstock, and a 3 in long neck pocket.
These numbers are on the same order as other guitar parameters, like string height. My MusicNomad Fret Rocker+ has marks 0.25mm apart to measure string height with, for example. Given that, it doesn't seem that far out to ask what the effect of a thousandth of an inch here or there is. To be clear, I'm saying the deviations I mentioned are
the reason for the discussed phenomenons, I'm just using it as an example of how we might actually be concerned about fairly small physical differences.