stenoglottis potting questions

[u bada]

I did a search earlier and couldn't find exactly the info I'm looking for, or I may have just missed it...

I have to repot a stenoglottis machloughlini, it's not overgrown, it just's because i didn't like the pot it came in... it's been sprouting and probably should do it sooon.

should I underpot? or is this something as a terrestrial should be in a larger pot to grow in? I had already pulled it up a bit and it's not a big root ball (it's young).

also I think someone here said avoid potting soil and use fine bark or I think I read even stone pebbles?

thanks in advance!