No 5th round replays from this season on.
Result decided on the day - extra time and penalties if needed.
http://www.thefa.com/news/2018/dec/18/fa-cup-fifth-round-replays-181218
I was there in the front (standing) part of the South stand, with my uncle and although he was on the stout side there was still room for a few more spectators where we were!