Hey LH, For downward tuning I string one of my guitars with a D'Addario J19 Bluegrass set. These are basically light gauge on top (E= .012, B= .016) and they get progressively heavier from G on down to .056 at the Low E string. This takes out the fret rattle on the low strings where it seems to mainly occur while leaving the top action fairly soft when I tune to Open D or Dsus. Of course, this depends on your set-up and action preferences.vl