I had a few pokies that also looked like that ventrally. They all turned out male. That whiter part is the concentration of the hairs where the female as a more even spread.
With pokies, the 2nd most accurate way to sex (Next to looking for spermecethae) is by looking for the dark line down the middle of the abdomen.
The carapace has a more even colour on the male.
But this does change over the course of it's life so if the T is very small, it is not very accurate.
Here is a good example of the difference:
www.arachnoboards.com/ab/showpost.php?p=1454484&postcount=9
What is the legspan of this specimen?
BTW. I am also thinking male.