My male BCI is about 2 yrs. old, at roughly 5' and a good weight (haven't been able to weigh him recently.) Now, my man's uncle has a female BCI
that he got the year we got ours, and she is HUGE.. I mean, she has a good foot on ours (or maybe a little more!) and is much, much girthier. I am betting this is just an obvious male vs. female growth rate, but he even feeds his less often (once every 2 wks, while I feed weekly.)
So I guess this could be a gender issue, as well as possibly a genetic thing? They are kept in similarly furnished and heated cages.