I discharged and charged all cells, and they all appear to be close to 6,500 mAh. I've spot welded a 4s battery together and just need to figure out how I'm going to attach my 10 gauge leads and balance wires.
Before doing this, I connected the battery in a very jenky way to my motorcycle and started it as proof of concept. No sense building it any further if it wouldn't start the bike.
I'm so impressed with the batteries so far that I placed an Aliexpress order for 12 more, along with a couple balance boards that are more sensitive than the 0.1v ones I've got.
My plan is to replace both motorcycle batteries with these 6.5 Ah LiFePO4, and the 4.2 Ah battery that's in the Acura's glove box.
These battery boxes are super cheap, but alas, they are too tall to fit in the motorcycle.
I'll post more photos and details as I build these things out. Been a busy month so far.
As a tangent, Tesla is now offering some Chinese made Tesla's with the LiFePO4 battery for the Model 3 SR+ Apparently they can fit these less energy dense batteries in the vehicle so long as they aren't a long range model.