I have been reading up on this a lot, but information on the internet is inconsistent or sometimes incomplete.

Some places say "length plus width should equal the boa's adult size," for instance. Other places say length by itself should equal the boa's size, then about 2 feet of width (or depth). Other places don't even differentiate between males and females, and just give one categorical size for all adult boas.

I'm planning to get a male BCI who is still pretty young, and I may have a very good deal on an enclosure that is something like 4' x 2' x 1.5'. Male boas evidently grow to be something like 4 to 6 feet long (the data on this is also not very consistent), so I'm wondering if this would be sufficient for a comfortable lifetime or if the boa is going to eventually be quite uncomfortable.