Thats exactly what I use braid for: more capacity. I like fishing mono, but need more line on my reels. So I figure out what line test I want to use on the reel for mono, then go a size higher in braid. I put 150 or 300yds (depending on what reel) of braid, and then top with mono. I do a reverse albright, or worm knot, and have had zero failures.
For the ABU 7000, if you fish it with 30# mono, I would get a 150yds spool of 40# braid, put it on the reel (make sure you put some electrical tape on the spool so the braid does not spin), do a worm knot to 30# mono, and then fill the reel to capacity with the mono.