I don’t think that you will have a problem adding vent on your molds because Canta 780 D has a DFS system and the Oticon 380P is analog so the feedback problem won’t be noticable if the vent is small and the ear canal is clean.
I don’t think that you will have a problem adding vent on your molds because Canta 780 D has a DFS system and the Oticon 380P is analog so the feedback problem won’t be noticable if the vent is small and the ear canal is clean.