Our largest is 5.5' long, and weighs in at 2900 grams. She hasn't eaten in a couple months, and is gravid.
She was a rescue we picked up. As far as we know, she's 10-11 years old. Her head is enormous compared to what I've seen in BPs. It's a mangled up head/face, too--much worse looking than your new girl.
Anyway, I dream of getting her up to the 5000 gram range. Congrats on your pickup, and hope you get her up really large!