Probably not the "best" option, but it would probably work just fine. You will definately need some ventilation holes either in the lid or in the sides of the container.
Also, how are you planning on heating the enclosure? I would hate for you to start melting plastic... but I doubt that will be a problem.
Also, sometimes the insides of those plastic containers can have sharp burrs left over from the molding process. Make sure to take a file or some sand paper to any rough or sharp edges before you put your boa in.
For what its worth, I place my Boa in a small tupperware conatiner when its feeding time.
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David - Houston, TX
Young Red Tail Boa
Purchased 11/16/03
www.geocities.com/davidag02