You would seriously need to do lots of research if you are going to breed. I can write you a book here, but it might take me awhile
They HAVE to be AT LEAST 6 feet long in order to breed, the female must be bigger than the male, and of extraordinary health. So, basically, breeding them this season is COMPLETELY out of the question (this breeding season has already gone under way). There is also quite a long process that goes into breeding any snake, you can't just put them together and expect them to start going at it.
Go to www.ssnakess.com ; they have TONS of info on breeding, BCI's, BCC's etc (Boa C. constrictor and Boa C. Imperator) Just do your homework, PLEASE! (I urge you!!) You'll have fun with it if you know what you are doing.
Also, if you are going to breed them, keep in mind that they can have anywhere from 4-60 babies at a time, and placing them may not be as easy as it seems. Not everybody is up to keeping a snake that will end up getting 10 feet long, and they only sell for about $60-$80 TOPS.
Please email me if you have other questions.

emroul@cox.net
Good luck,
Jennifer