I agree with Craig, but I would add that, in addition to personal comfort, you also have to consider the type of stream you plan on frequenting and the specific kind of fly fishing you prefer. Some of those blueline streams can get pretty claustrophobic - especially in the summer - and even a 7' rod will seem way too long for highsticking, while most of the lower elevation streams offer plenty of wide open spaces where you'd feel comfortable high sticking a 9'6" or even longer rod. And, if you prefer the precise, delicate presentation of a tiny dry fly to dredging a nymph on the bottom then you'll probably be better off with a shorter, lighter rod.
That's another great thing about the Smokies -- diversity
If I'm spending the day in the mountains, I'll generally take two rods with me: an 8' 3 wt for fishing dries up high, and an 8'6" 4 wt for everything else. That 3 wt. is no good for nymphing or trying to fling dry/dropper rigs but it's very good at placing #20 BWO's right where I want them. My 4 wt. can handle everything else!
I may be wrong, but if you've been fishing a 7' 4 wt rod then I'd guess you prefer delicate presentation of a dry in close quarters. If not, then I'd guess you've been using the wrong rod all this time and you're just about frustrated enough to give up on the sport