Oh yeah, I forgot that your battery started with 2 cells, but you separated them. I will probably attempt something similar, but with the batteries that @SchattengestaItbought.
I haven't taken my Pro1 X apart yet, so I won't mess with that. I will probably take the bms and connector off the MI 6 battery I bought for testing with my Pro1. I proved that it would power the Pro1. I still have that phone taken apart. We'll see if the BMS likes the new batteries and how the plug orientation works. This all assumes that the new batteries arrive on their long journey from China.