Thanks for all the responses re: batteries.
I have the 3400mah batteries, so I have the "new larger" batteries referred to by the OP. Wasn't aware that those are recent/newer, because I'd been out of Phase One systems for quite some time until recently with the XF/IQ3100.
While I do find the power provided by the 3400s to be adequate, especially with power sharing, I'd sure like to see a higher power/longer lasting battery, so that - at least with the power sharing feature - I don't even have to think about power levels (which is the case now with my Nikons: no matter what kind of shoot I have planned, once the batteries are fully charged, I know I don't even have to think about power levels while shooting). I fully realize that medium format backs and bodies are very power hungry, so there may not yet even be a battery solution that provides a duration of battery power equivalent to the small Nikons. But right now, I have 8 of the 3400 batteries and feel the need to keep them all charged at all times and to keep *at least* two backup batteries (in addition to the 2 in the camera) on hand during a shoot.