The Batteries Have Landed
I've spent the last couple hours soldering them together in sticks of six volts (5 cells). The solder tabs make this relatively easy, and the heat shrink tubing should enhance the conductivity by forcing the cells together:
I still need to solder on the interconnect wiring, seal the ends up with silicone, and position the thermistor for the charger's temperature sensing. Plus I'll need to figure out how I'm going to affix the pack to the board. I'm leaning toward using the industrial-strength velcro that held the previous pack in place.
Finally it will need a full charge before I taking it for a test run around the block.