off the top of my head.....i don't know...
But....what kind of tool are you trying to use? A socket?
Honestly I didnt have to adjust my truss rod in my warmoth neck!! I have the boatneck or Louisville Slugger profile, which seems pretty stable!!
Anyway... What I would recommend is a trip to Sears. What you are looking for are 6 POINT sockets, not the 12 or 16 point sockets they usually put with their 'mechanic' sets. My dad bought me a set of six point sockets a couple years back and honestly they fit into way tighter spaces because the walls of the sockets are way thinner than the sockets with more points. I will tell you that I have broken a bunch of 19mm 6 point sockets removing wheels on my truck and my wife's car (that is the lug nut size on both) but usually I break them because I am impatient and don't get out my impact sockets which can take the abuse. The six point craftsman sockets don't hold up well to an impact gun! Great thing about Craftsman tools, warrantied forever. Anyway, try that, unless you already have 6 point sockets and tried that, then I don't know what to tell you. Also you want to find your socket in 1/4" drive, those are the thinnest and smallest sockets they sell. If you are trying with 3/8" drive, the wall might be too thick.
Truss rods sometimes are tough to get a socket or wrench on. I have a carvin neck also, which is the only guitar that I have ever owned that needs constant truss rod adjustment, and I use a little tool that came with an old pair of Rollerblades..... hey it fits, not well, but it fits. It's sometimes really tough to get something on there square so you don't end up knocking the corners of the nut off. I have been meaning for years to open up the truss rod adjustment hole with the dremel so I can get my tool on there square, but that would entail, well, IDK, I like frustration :icon_scratch:
Sorry I didn't answer your question per se but maybe my tip can steer you in the right direction :icon_thumright: