I pack all my 50's with Hi-Vis 80# test. What you lose in capacity, you gain in strength, but more importantly, abrasion resistence. The Hi-Vis allows you to see your lines in the spread more easily than clear or other colors.
Think about using 130# spectra for backing, about $60 for 600 yards of Cortland Spectron on the web; this brand is hollow in this size and you can use smooth, loop-to-loop connections. No knots! You'll get 600 yards of backing plus 200 yards of 80# mono and you only change the topshot.
You don't have to go to braids to get good capacity on a 50TW. Just pick a thinner 80# line. Berkley Big Game should get you app. 595yds. Tight Lines (Bass Pro)app. 565yds. and HiSeas Black Widow 590yds. pack it tight and maybe get a little more. I just put a measured 480yds. of 80# Tight Lines on my 900H Yeah it was a pain in the A##, I ran it back and forth my back yard from fence to fence.