Sorry you haven't had more responses yet. Having no frets, I've never had to deal with this problem, but just thinking about it in abstract terms, I don't see why the truss rod tension should matter much (if at all), and I would be inclined to just leave it as you like.
If you were going to take several days or weeks to do the job, then you might want to relieve the tension once you had removed the strings. But assuming you are going to do it in a short period - and get back to playing as soon as possible - then I see no reason to mess with the truss rods.
Maybe I'm missing something, but if tension really does make any difference, then I would think you should do the filing with the tension on.
Just to be clear, I assume you are filing off protrusions at the ends, beyond the fretboard. If you were instead leveling the frets, then you would certainly want to do that with the neck perfectly straight, but I don't think that's what you're asking.
Good luck.
-Bob
(Message edited by bob on September 21, 2005)
