[charles Tauber]

I don't really have a need for a fret rocker. Playing notes at specific frets, listening to the response and sighting the fingerboard tell me what I need to know. If you want to use one, and that is YOUR preferred method, fine, go for it.

If the fingerboard extension is floating and not rigid, you're likely to have recurring problems with fret buzzes if the geometry of the fingerboard continuously changes. (The reason that fingerboard have historically been glued to something is to ensure that they remain rigid and stable. My experience has been that the sound of notes played on un-fixed portions of a fingerboard have a different tone.)

As you've described it, the 16th fret is too high compared to the 15th. To check if fret ends, in particular, are loose and sticking up, I use the end of 3/8" wooden dowel to press down on the end of the fret and see if the fret moves. (The end of a pencil will also work, with or without the erase on its end.) If it is loose, it can be glued back down, while holding it down with the end of the dowel.

You might be able to successfully spot-lower that one fret, but, doing so, as Roger noted, might just have you chasing high frets up the fingerboard. Usually, I'd dress all of the frets in the area to ensure a true surface across the tops of the frets. You might also like to sight down the neck towards the soundhole, and/or use a straightedge, to assess the flatness of the playing surface, in general. If the soundhole end of the fingerboard - the unglued area - sticks up, that might be the issue and the 16th fret just a symptom (i.e. where the change in geometry occurs).