I don't have any first-hand knowledge either, but according to "Hiking Trails of the Smokies" from the Road down to #53 you will lose about 1750', which of course you would have to make up on the way out. But across 3.9 miles that isn't too terrible of a gradient (Although the last 1.2miles look steep - 800'+).
According to the book, #53 is right on the stream and in a pretty setting, but heavily used and rather unappealing (whatever that means). #54 is away from the stream and is another 2.5 miles further. Unfortunately #54 is closed due to Bear activity. #55 is a rationed site and is 7.4 miles from Newfound Gap Rd.
It sounds like #53 will be your best option. And if the water is too low, you could hike down a bit and fish your way back up to it. At about 4.7miles the trail moves about 200' above the stream but rejoins it a little ways down further (less than .5miles?), but other than that the trail seems to more or less closely follow the stream, once it joins it (at around 1.1miles from the road).
According to Don Kirk's book, you should see Brookies above 3600', so the first mile after you reach the creek (at roughly 4000' elevation), may be your best bet for Specs.
Make sure you keep an eye on the weather, it looks like we may get at least an inch of rain over the weekend. It also, looks like the NC side of the park has had less rain than the TN side, this past week.
Let us know how it goes. The more I look at it, the more I want to give it a go, as well.