Congrats on that fish, sounds like you are having yourself a heck of a year. That kind of finesse (8#) is not what most anglers would consider conventional for the fishery (which was my point). I wish everyone gave as much consideration for the "sport" in sportfishing as you.
On an unrelated note it's possible to go too far on the light side as well, which is a common accusation made against fly fishing. Despite these claims I'm confident that with 9wt or better gear and an aggressive fighting method the fish is in good shape when it takes off like a rocket after release. This applies even more to today's awesome light tackle spinning and level-wind outfits, with fast retrieve rates and silky drags light tackle tames big fish efficiently... as Sully's fish proves.
That being said, as a fly-only angler I think I'd pop 8# tippet every time with fish over mid-30" range trying to get them in for a quick release. I use 12# for light tippets (flats) and 15# for heavy (rips). On occasion, I will use 20# in the big surf (e.g. Nauset) to land big fish in the pounding surf effectively. Fly size also plays a big part, I will override as needed to turn a big fly over.