Using the Ronin 2 with the stock setup of the Dual Battery Mount mounted on the top of the gimbal, is it possible to use a 2nd Dual Battery Mount and plug it into the the top of the gimbal with the auxiillary power cable also? This would give me 4 batteries and an extended run time. Or does the Ronin on allow one of the power inputs to be operational at a time?

Two batteries power a camera (red) with accessories and the gimbal for a long time ... and you can hot swap them. I guess you are not going handheld but trying to mount
on a car or crane where it´s not possible to access ?

there is this thing for inspire2 ;) ... not sure if it works  :  https://charger.nitecore.com/product/dpe1

also TB55 work on ronin2