the router leaves a rounded end, so I went back in with a razor chisel and a scraper to square the ends
so, now the channel ends are square
the business end of the truss rod is 1/16th wider and deeper, so I nudged the fence on that end a bit, and moved the stops to that 2" section, and finished that cut very carefully. I had to spend a bit more time with a chisel and exacto to get it perfect
.... but perfect it is.
So that's done. Next thing is gluing on the fret board. Which means the next thing is planing that down to 1/4" and sanding or planing a radius onto the surface.