Growth rate is not a good indicator of sex. i have 2 B. hamorii right now received from the same source at the same size One is now twice the size (kept under nearly identical conditions) and the LARGER one is female and the male is taking his sweet time to grow...
The areas to examine when vent sexing are the pedipalps (quick check to make sure its not a MM. if it isn't a MM then the area of the epigastric furrow is examined. Some people look for the male sex organs (epigandrous fusillae <- probably spelt wrong). If present the specimen is a male.
Others look for a 'slit' or 'vent' which is the opening to the uterus exturnus of a female. If there opening is there it would be a female, if not then male.
I do not consider myself good at vent sexing but i agree with Kezy (whom is much more experienced than myself)
Not sure how Kezy does it, but I tend to have better accuracy looking at the 'vent' than looking for fusillae (probably spelt wrong again). I believe the vent looks female and i see nothing i believe to be the fusillae.