It depends on where you the think the master record is being held.  If Indicia is just being used for data capture (which is the way some users see it) , then once the records have been transferred to R6, then they shouldn't be transferred again and all corrections made in R6 (and also in Indicia if you wish, but R6 would still hold the master record).  In this case it doesn't look like the addin will be the best way and you would be better off using the import wizard. I assume that you can get the data  out of Indicia and that will include the record id which can go into the External reference implemented in 6.21.     

If you think the master record is in Indicia then it looks like the Addin will be almost the same as importing them from another users copy of R6.  In this case you will not be the custodian and not able to alter the records in R6.  Validation and changes should then be done in Indicia and the records imported again - not sure here what happens in Indica with deletions ?  You would stil be able to add new determinations as with an import from another R6 user, and the Indicia import seems to deal rather better with retaining the preferred indicator than R6 does.

Alternatively, you could import the Indicia records as temporary data via the Import Wizard. The idea being that occasionally you delete the the whole Survey and replace it with a new import. The master record woul remain in Indicia so data imported in this way could never be exported. You could manage this by importing new records on a regular basis and now and again refresh the whole dataset. Version 6.21 of R6 facilitates the import of temporary data in this way. Some users might prefer this approach as it allows the data to be fitted into existing structures, without adding new recorders etc. Also corrections can be made if required, although these will be lost when the data is reimported. Refer to v6.21 Additional Notes for more details on this. http://forums.nbn.org.uk/viewtopic.php?id=4926