I added a top shot of 65lb. braid to two of my reels, that had 50lb mono this fall. Used it to run the short ,deep, boat rods pulling umbrella's.
One 300yd spool for the two reels, 150yds per. I used a cheap line counter, 15 bucks at almost any Tackle store to take 70yds. off and put a 150 yds on the first reel. Problem was, the uni to uni knots tag end tit will tlegraph thru, making it rough on the thumb when letting the lines out. I would follow the advice above and add more than the 100yds. As a side note, amazing how deep the braid runs as compaired to the mono, at least on the heavy deep lines. I never did get them dialed in, as far as depth, and never hooked up in five trips out after changing to braid.
We snagged both lines second trip out in forty feet of water, maybe a net, but there was no getting them up, hooked rock hard, so backed down and cut them. If I was to do it again, I would still add at least 150 yds, maybe three hundred each.