I ended up choosing pingping as a battery source, for now. I've got a 24v10ah pack in hand and a 36v10ah pack is on it's way. The 24v pack is going into my Charger bicycle, while the 36v pack is going into my Electra w/ WE BD 36v motor.
I have only taken a first look at the pack right now. The Charger bike has a large plastic battery box that mounts in the center triangle -- not to water bottle mounts, but to a mount specifically meant for this battery box. The frame is custom designed ..
I weighed the batter box with the SLA batteries -- they are 2x 12v 12ah batteries, and the box weighed 26 lbs with the batteries in them.
The pingping 24v10ah pack is almost exactly the size of one of the 12v12ah batteries -- that makes the pingping pack exactly 1/2 the size of the equivalent SLA pack. That also means with a small bit of modification the pingping pack and charger will fit within the box. I just weighed the box with those two inside-- it came to 11 lbs. Or, about 1/3 the weight.
I am astonished, and cannot wait to see what this is gonna be like. I found the Charger bike unpleasant to ride because the pack weight made it seem like I was riding through molasses. So, heck, with this lighter pack.. WOW. I might end up riding this bike more often.
1/2 the size and 1/3 the weight. Ohmygosh. It's coming true.