My $0.019 on the neck dive thing with Roger’s chambered body instruments:
It is true that the chambering to create the ultra light instruments, which Roger has developed, also changes the instrument balance on the strap. The “neck dive” associated with this design aspect is a consequence of the design; but, it is much less significant than some other higher end instrument designs. My Alembic Series I SSB comes to mind.
Since the chambered instruments tend to be very light, mine is less than 8 pounds, the slight imbalance is easily negated by using a strap that is just slightly “grabby” on underside. For example, I have a Levy’s strap with a suede finish which locks my NYC into playing position. The bass is so light that the moment of inertia created by the balance aspect puts negligible torque on my shirt or shoulder. So, the imbalance is simply not an issue.
That is what Roger is referring to when he recommends getting a decent strap. And, if you think about it, spending an extra $75 on a decent strap for a $4k+ instrument isn’t all that out of line. I suppose the problem might be that a lot of straps have a smooth tanned underside; and those straps can allow the instrument to rotate if you are standing at the mic clapping on an intro etc. Like that ever happens (guilty here).
Anyhow, as usual, Roger’s advice on the topic is consistent with my experience. Get a decent “grabby” strap. Issue solved.