Covering hair once married.
The other day I saw that the Tzitz Eliezer in his Sefer on Yichud (6:39; I think this was in Perek 22 or 23) that he brings down not like I said. He quotes from some Poskim that N’giyah would be Muttar in a case where there is no physical possibility of Biah whatsoever (e.g. if the man is old or sick and therefore impotent). However, I still stand by what I said that from the Stimas D’varim of the vast majority of Poskim we don’t make such a Chilluk. Still, I was remiss in assuming that no one disagreed with that fact.