:As long as you can provide him with the correct temps and humidity, he will do fine in the adult enclosure. However, it certanily is easier to control temps and humidity in a small plastic sweater box than in a larger adult enclosure. :
Babies may also become stressed in larger cages than in smaller cages. I have several that are going on the two year old mark, and most have adapted to adult cages. Mind you, these chondros are over 3' long and feeding on adult mice. I still have a couple that refuse to do eat while in large enclosures. They not only refuse to eat, but will hide under the paper 24/7. I would keep it in the tub until it gains a little size. It's much easier starting out.