Tubs aren't that expensive, so I would gradually increase the size of the enclosure. Just remember too that the smaller the tub the easier to maintain temps. Now for a snake only 2 feet in length? Well, that's still pretty small, so don't go crazy. If it's large add lots of extra hides and maybe some vines or newspaper balls to it. I don't know that that was much help....

Are you wanting exact measurements?