When connecting the input and return buses from multiple BDFB panels together you only need one panel with digital metering (P/N 007-0001-2602).  Since the buses are connected, each panel's digital meter would provide the same reading so only one is required in the chain.  

The panel that includes the digital meter requires a shunt kit for proper operation.  In addition, in order to use the Current Test Jacks on each panel a shunt kit is required for each panel.