Jack looks pretty good to me.
How often are you feeding him and what are you feeding him? Do have a good weight on Jack?
He looks beautiful and healthy to me.
I have a female Ivory Ghost BCI, Behira, but she's only 2 now. However, from seeing enough Boa's, he does look pretty squared and happy.
Males are rarely as thick as females, so make sure if you compare him to another BCI, it's a male, not a female.