Hello,
I can only speak on my experience, but i've got my 2m integrade in a 4' x 2' enclosure.
He will be upsized if/when he grows some more but at this point he is more than happy in that.
The NSW code of practice has some guide lines if you want to check it out; I think they are reasonable for python species. You can find it through google or the search bar here.
Cheers, Amber