There are some wonderful threads on this
I would personally give them as much space as you can. They love to move around, a lot. Right now I have a T8 and a T10 from Animal plastics.
Their sizes
T8 - 4’ x 2’ x 1’
T10 - 4’ x 2’ x 15”
Nothing is saying that a 5’ x 3’ x 2’ won’t work. Boas can get big with age so always be will to upgrade as necessary.