There's got to be a slight bend in the neck of an acoustic guitar when the strings are tightened. Fret it at the 12th fret and the first fret, and you'll see the strings aren't touching the fret half away along the neck. 16th of an inch clearance, or round about that, but it varies from guitar to guitar.

That's the kind of amount of bend which a non-pro can fiddle around with getting exactly right, and it drives you crazy doing it. Or it does me, because the only way I know to do it is restring the guitar and tune it up; and if it's not quite right, loosen down all the strings and fiddle with it a bit more and so forth.

So if anyone's got any advice about short cuts and wrinkles, I'd be grateful. But if there's a significant warp, for God's sake don't go messing about with it yourself.