c100:
My regulator: you cannot start an RNP AR APCH approach without Dual GNSS but after the FF you can continue with a single GNSS.
That's fine for some circumstances in more conventional instrument flying, but entering the final segment in some RNP AR approaches (say RNP of .2 or less with an RNP required missed approach) is literally going into an area where extraction should be the rule when any significant part of the avionics fails.