I use 700Yds of 100# power pro & +-200 yds of 60#-80# mono top shot, on my 50SW's
If you are going with only mono you want as much as you can get on it, in that case go with 50#.
Don't be scared to put the heat on her, up to 22# of drag, if she is stripping you.
Better to lose it in the first 20 min. than lose her after a few hours.

irat:
Opinions will varry