OK,
Look into the Darwin or IJ carpets. Usually even the bigger carpets don't girth out like the boas. And,,, my understanding is the BCA boas, while not really long can be quite thick.
I think once you see a 6 foot slim snake is not much to handle, you'll be OK.
Length without the thickness really is not too intimidating. However when the female boas start putting on the girth, they become a lot more to handle LOL!
Handle a a BRB and a carpet, look at a few and see what you think. Choose carefully and don't rush.
It's a fun hobby and it sounds like you are in the driver's seat right now. Get what you want !!!!