http://bmxglider.tripod.com/maleorfemale.html
I had a male that had his bald spot and 16 weeks/4 mos. There have been others that haven't had their develop until almost a year. If they are neutered, chances are they will not develop one at all. Yes, the testicle sac (poms) are located mid-belly where the pouch would be and looks like a little bunny tail. Again though, if neutered, it may have been removed. With females, it's kind of hard to see the vertical pouch until they're a few months old. You can usually get a good look if you can get them onto the side of the cage right in front of you. Maybe have him/her reach up for a treat while you're looking so they stretch out in front of you. Hope that helps!