Interesting Poll - Almost every time I fish the upper Delaware I see the backing at least once per day. Big fish, big river.
On a recent discussion on reels, most were of the opinion that a reel is just a spool. I interjected, big river, big fish, you need a really good reel (afer two 23" browns in one day I sold my battenkill and bought a ross evolution). Most disagreed with me.
What do I mean by really good reel. Great drag, low inertia to start reel. Whenever I have been into the backing it was a 20" plus fish, typically 7x tippet, sometimes 6x, never bigger. While I was nervous the first time, I am now confident when I get into the backing (but happy when I get the line back on the reel).
This is on a sage 5wt, and a winston 4 wt, mostly the 5 wt on the Delaware. Interestingly last year I caught and released three 18" rainbows inside of approximately 15 minutes on DePuys spring creek in Montana. Ankle deep riffles. One of those fish on the Delaware would have taken 15 minutes.
Quoting Jason Borger, from the "Nature of Fly Casting"
"keep in mind, however that a fish like a 20 inch rainbow may never pull out more than 10 yards of line in small waters, but that same fish may run 50 yards in a big river or lake"