That holster looks very nice!
Regarding stitching, although I certainly don't have the experience of most of the people who have already weighed in, I chuck one of my harness needles in my drill press to make my holes--no leather removal, very precisely sized, and they close up tight. That said, I don't put both needles through at once *gasp!*. I know, I'm a blasphemer, but I pull one needle through and then the other needle through and pull them tight together. It's a little slower than putting both through at once, but it keeps the holes as small as possible and I have found no difference in effectiveness or evenness of my stitching by doing it this way and it works for me, so I'll keep doing it. Just an option