Hi Saurabh,
You do not need to create the subversion STFI01. Just take the INVOIC D 96A message and copy it to a new Ctrl Key (if you want to modify the existing ctrl key). Then you take the payload with STFI01 and it will be treated as EDIFACT. This message will not be processed as EANCOM and you need to have EDIFACT settings everywhere in order to process this.
Best Regards,
Ruchir