I don’t mean to buck anyone else’s advice, but I will tell you my experience.
I have a Boaphile 322 being used as a quarantine cage for my Olive Python. She is a skinny baby/juvie at 4.5 feet and already outgrowing it. I would not even consider putting my adult BP in there.
My BP is in a 4x2 and has some breathing room.
If you only want to buy once, I recommend the 422 even though the 322 will work for now.