It occurs to me that in metrical poetry, there is an exact equivalent to "confidence of line," one that could almost be called the same. There's a difference between a poet who knows meter and is making sure his syllables fit the pattern, and one who knows the rhythm in her bones and says something with that soundshape. One key determining sign: never seeing any awkward phases to fit the form. When you get to the confidence of line stage, you can start writing with and upon and against that pattern, playing with the line.

---L.