Don't get discouraged it just takes time and patience. I'm still working on mine. I know there are way more experienced builders on here than me but I will help you out in what ever way I can. I am making the soft / leather parts myself. I'm on my second vest right now been working on it off and on for about 2 months now. These are the ammo pouches that I made.
http://www.thedentedhelmet.com/f28/jango-build-leather-working-questions-54214/ I still haven't made my girth belt yet so you are a few steps ahead of me but Cruzer has a great tutorial on here that I will be using to make mine.
What is the height measurement of your Ammo Pouches and who did you get them from? Also wondering what is the width of your belt that goes with your ammo pouches?
Can you post a picture of your girth belt (showing the two ends that need to attach together)? Don't buy a new one yet not until you know for sure that you need to. The girth belt is a little pricey.