I have an Essex short scale whose truss rod appears to be bottomed out. By that, I mean the truss rod is functional, but will not flatten out the neck as much as I would like when completely tightened. From what I understand, this can happen when the threaded nut or plate on the body end of the truss rod (inside the neck) crushes the wood against which it bears, thereby reducing the rod's potential, over-all, effective travel. The bass in question is currently strung with light-gauge, round wounds: .036"-.054"-.062"-.088" (according to my calipers). Certainly nothing excessive which one would expect to overwhelm the truss rod. Of course, I don't know whether the previous owner used heavier strings in the past. When I got the bass, it had already been adjusted to the point where there was not more that 1/8 of a turn left in the "tighten" direction. When I lower the action to taste, I get fret buzz when playing in the upper registers (above 10th or 12th fret) unless I play with an EXTREMELY light touch. With a truss rod that has a nut on the headstock end (under the truss rod cover, like a Gibson) the solution is supposedly to remove said nut and add spacer washers under it. But I'm not sure how something equivalent could be done with the SX truss rod, which is a rod with a (female) hex on the headstock end, rather than a solid rod with a nut on it. If I have a correct understanding of how these truss rods are constructed, I assume that the round collar (visible inside the truss rod hole, headstock end) of the Essex, through which the rod itself seem to pass, could also be shimmed. But that would require completely unscrewing and removing the entire truss rod, leaving the plate on the body end of the truss rod route still loose inside the neck. My concern is that I worry that once the truss rod is shimmed and re-inerted in its hole from the headstock end, that it might get cross-threaded in the plate at the body end (since there is no way to hold that square to the rod as it is re-threaded. If I am misunderstanding how the components of this Essex truss rod are constructed and how they fit together/function, or if I am over-looking some easy solution, please school me, as I am obviously no luthier (though I have managed to perform serviceable set-ups on my other basses, none of which suffer from the malady outlined above). Thanks in advance.