I'm happy to report... the battery pack appears to be happy once again!
I just got back from a ~75 km (~47 mi.) drive after re-installing the battery pack in the car. Here's what happened:
- I cleared the existing "check engine light" code (related to the battery) left over from last time I drove the car
- Before starting the engine, the dash showed 0 out of 20 bars on the battery gauge (ie. "empty"), despite having topped up all 20 subpacks/sticks one last time with the SuperBrain yesterday.
- After starting the engine, the dash showed 4 / 20 bars of charging while idling (if you don't know what that looks like in an Insight, see photo below)
[
Battery pack charging @ 4/20 bars - doctored photo 
]
- The 4/20 charging @ idle lasted for just a couple of minutes before the battery gauge suddenly climbed from 0 to 19 bars (within ~20 seconds), and charging ceased.
- Then I went for a ~75 km drive. I intentionally pulled multiple high-current discharges (using assist: accelerating up long hills; multiple accelerations from rest up to ~120 km/h / 70 mph onto the freeway; multiple cycles of top gear maximum acceleration from ~50-70 mph); multiple recharges (extended maximum braking regeneration on off-ramps & coasting regen down hills).
- The battery gauge never dropped below 16 bars, and never went above 19 bars.
- Most importantly: the check engine/IMA lights did not come on
Previously, ~20 km was the farthest I could drive the car without causing the error lights to come on, driving
very conservatively. So, I'm calling this a successful "rejuvenation".
Next step: installing the grid charger to keep the pack balanced in the long run.