Hi Daniel,
I don't think you want to practice in one way to play in some other way once
you're good enough. Life's too short, I'm afraid.
I would recommend the beginner to try to develop good habits starting from
0, and in that direction, I don't think that any part of your body should
be rigid or stiff when playing (or practicing), and very specially your
fingers.
For an ex- guitarist, who cannot keep little finger on the top for one
second, I would advice some specific training, that doesn't only have to do
with the finger itself, but again: there's no way you can get to play more
or less satisfactorily the whole literature without being flexible and
consciousness or the importance of relaxation.
Saludos,
A
