They tend to be, but from what I've seen they can ALL get to be about 6 feet given enough time, except for the yellow head blacks which stay much smaller. I've only heard of the reds getting 8+ feet, though.

The blacks and Borneos have a reputation for being the best tempered, but there are well behaved reds, too. Just work with it from the start, and stay away from WC animals. Some breeders even breed for temperament and should be able to select a calmer hatchling for you should you request it, so that's something to look for, too.