Yes, you can use the backing to play a steelhead. In fact, with the normal size 14-16 hooks and 3X-4X tippet that we use, you should count on it. Modern large arbor reels hold the same amount of fly line as conventional reels, but the extra capacity is there for - backing. I use two colors of backing on my steelhead rods. The 100 yards of outer backing connected to the fly line is chartreuse (fly line is ivory). The backing tied between the spool arbor and the outer backing (maybe 30 yards or so) is fluor red . If I am playing a fish in the chartreuse backing, it's OK. But if the fish gets me into the red backing, it is time to break him off, chase him, or just pull hard and hope. Note that good arbor and Albright knots are essential. They should be retied every season and checked every few trips.