The H2-ECOM100 is a DirectLOGIC module when interfacing with DirectLOGIC protocol or Modbus/TCP protocol (but it also supports the Do-more protocol). Hence, when it gets a Modbus request, it utilizes the infamous Modbus Mapping mechanism of the DirectLOGIC PLCs. When the ECOM100 receives a Modbus request via the Ethernet port, it does the Modbus->DirectLOGIC mapping then actually does DL requests across the backplane (not Modbus, not Do-more). The Do-more PLC, seeing the DirectLOGIC request from that slot, then maps those DL protocol requests into the specific DLV, DLC, DLX, or DLY memory in the Do-more.
You can expand the DLV, DLC, DLX, and DLY memory in the Do-more to as large as what the DirectLOGIC PLC supports (anything larger is not addressable via DL communications).
If there's any area of "V" memory in the "spreadsheet" that maps to DL's Stage or GX/GY memory, that area is not supported by Do-more. I do not have a link to that Modbus/DL Memory spreadsheet, but someone else can probably point you to it if you do not already have it.