Worried about Data Loss while changing extract structure, why not try this?
Run the Report RMCSBWCC before doing changes to the LO extract structure or while importing any changes done to the extract structure.
This report checks whether any of the clients in the system contains data in the V3 update (Extraction queue) for that application (specific to extract structure provided as input). If there is data in V3 updates then you need to start the update for that application. Without doing this you will not be able to change the extract structure and if you are importing the changes then you may end up losing data.