Thanks for taking the time to answer, Rick!
Yep, I knew about this label thing from Frank Ford, I actually learned it here at the agf. I've used it before in other guitars and didn't feel a difference in tone. I understand that over time the strings wear down the slots (don't know if the treble strings really do) and that's a neat way of slightly raising the action.
You're right, many variables involved. But I guess this tolerance of a piece of paper is acceptable then, as the guitar is not buzzing.
I've always tried to leave a moderate gap because, being nylon strings, there's more tendency to buzz.
But now the string height at the nut is basically setup just like a steel string or an electric guitar. It gets me wondering if nylon strings really need that much of a gap at the nut.
Btw, I forgot to mention that the strings I'm using are Daddario's Pro Arte Normal Tension.
PS: thanks for the advice Rick, but I don't order from Stewmac nor do I have a credit card
I don't live in the US and buying imports here is really out of question because of taxes (it'd get about two or three or times more expensive just because of them).