I do agree with everyone that it may be a bit large to start. I would like to give my experience though.

I recently bought a couple babies myself. Both '11's. I had one in a homemade enclosure that was much larger than 40gal, and the other in a 20g tall. ( all temps and humidity are good for those wondering =P ).

In the large homemade enclosure, there were a total of 4 hides, and 1 ledge higher than the lighting. Plenty of fake plants and decorations. Lots to climb on and crevasses ( that weren't hides ) to hide in. He was eating like a champ. Liked to climb around and 'explore' at night. Would hide a lot during the day ( of course ). Never defensive or showed signs of stress (after the first day or two or anyways). I did recently move him into a smaller enclosure to put my '09 female in the bigger enclosure. He still eats great with no issues.

The other baby in the 20g tall has 2 hides and some other decorations. Same deal. Never defensive or showing signs of stress. Eats without hesitation.

I am by no means saying that you should house a small snake in a large enclosure, as it 'can' lead to stress. I am just giving my current experience in it. I have never had a problem as long as there were plenty of places to hide. If you do decide to keep the larger enclosure for the little one, I would just make sure to add more than 2 hides in my opinion.

My $.02