A 56-year-old patient consulted a prosthodontist about pain underneath the bar of her clasp prosthesis. It is known from the anamnesis that the clasp was placed in another city a week ago. Examination revealed a mechanic injury of mucous membrane of the palatine vault caused by the bar of the clasp prosthesis. What distance should exist between the palate and the bar of the clasp prosthesis in order to prevent this complication?