FWIW, I figured out four days ago it was just easier to play John's part on my Persuader 5-string that all that detuning and retuning, and trying to keep straight in my head... okay, fourth string, third fret is now an F..., and recalibrating from there. I have enough sense of pitch that my ears won't lie to my brain and tell it that it's actually a G, so... too much of a headgame. I don't know how Johnny-Mac did it.
At this point, I'd like to extend a little 'Thank-You-Sir' to Jimmy J, for the B-string short-cut. At least, the Alembic one.