I have another classical, which I rescued from the dumpster, because I wanted to try putting steel strings on a classical to get the wider fingerboard. So I got this almost free ax to try it on. It was made in China by someone who did not know what a guitar is supposed to do. The neck leaned back 3 degrees or more, the strings were laying flat on the frets. Adjusting the tension of the steel rod inside did nothing. So I ran it thru my table saw to separate the heel from the body - be bold! no risk :) and drilled a hole thru the heel for a bolt. So now the action is adjustable by tightening the bolt.

FYI, the sound is outstanding. The steel strings have more tension than nylon, and the top of the ax is distended like a rolling countryside, but it didn't tear itself apart (yet). I played it at the church picnic a week ago and I was impressed by the good loud sound in a big open space, largish crowd.

OK, so here's the interesting part: this configuration gives the neck a little flex. So when I'm tuning it up, say I tighten one string, the other 5 get slightly looser. I believe this happens to a microscopic degree with all guitars.