i don't think you have to worry THAT much about size... most only get around 6'. the most common captive species, the taiwanese stripe-tailed rat snake (Elaphe taeniura friesei) has a record size of only 7'9". there's a breeder not too far from where i live that has bred them with some regularity and i had a lengthy discussion with him at a show last fall.
they're a nervous snake, but most are very temperature tolerant because of the mountainous regions they are from. i suspect that if you get a CBB very young neonate you should be good to go.