Oh also Ziggy, you arent going to find too many boas that get to really large sizes. About the biggest will be Peruvian BCC which would probably top around 10 feet but you are looking at about 10 years for that lol. Boas grow very slow compared to pythons.
If you are looking for size, then you will probably want to stick to pythons like a dwarf or SD cross. With retics, there are tons of stuff. Or if you dont mind a possible 13 foot male, you got even more choices with mainlands. For darker stuff, look at super Motleys or Goldenchilds. Also there is one i personally like, Mochinos.