Be careful if restringing or retuning drastically, otherwise you could end up doing some damage to the instrument or make it difficult to play. Use a string tension calculator to work out the current tension and what it would be once retuned and then choose the appropriate gauges to bring the tension back to what it should be - does this make sense?

With respect to styles, octave strung is fine for chordal work but can sound a bit strange when playing melodic stuff - well in my opinion it does!