just trying out a new design for me...
Layout: I use one of two different tools to set my stitch distance. A Compass set at just under 1/4 inch or a plastic stitch guide with holes at the same distance. It looks like a clear sheet of plastic with a red lined graph paper pattern on it...
Holes: I used a Scratch Awl I have ground to a Diamond shaped point or a a smaller sewing fib to punch the holes marked out before hand. I do the front side first and then lay it over the back side and punch it a second time through the front.
Before Sewing: I glue all flat areas where front and back come together then sew.
Sewing: Is all by hand with waxed linen thread and I do four passes with a locking stitch making sure if a thread breaks in a spot it will not com apart.
I when I am sewing something, I will often scribe a line with the compasses, then follow that with a stylus to give me a small groove to lay out my stitch pattern. I use leather chisels to set the distance between holes, but a stitching (layout) wheel is also a good choice. I too will punch the holes in the top then lay it over the back and punch through the holes this assures that they line up properly. Your stitch guide is good, but seems like extra work to me. I have never tried one so I may be wrong there. Yes, the double punching does seem like extra work, but it is the only way I have found that really works. I have tried doing all the way through both pieces at once, but that only works on lighter weight leather. I have had threads break on some of my projects and had to pull a few stitches out so that I could work a locking stitch at the break. But most of my stitching is done using what they call a saddle stitch. When you look at it, it looks like it was done on a sewing machine, but if you cut the thread somewhere and start pulling it apart, it is actually two strings that criss-cross in the holes, then again in the next hole. I haven't tried holsters yet, though I am thinking about it. I really like the look of yours, I just can't figure out how to use the sewing awl. The saddle stitch is somewhat intensive but it is also one you can put down if you have to and come back to later and you just have to pick it up and start where you left off. The other issue with it is that you have to have at least one pair of needle nose pliers and two don't hurt to pull your needles through.
You may have already tried these and found that you like the way you are doing it now better. That's great if you have. If you haven't already tried this, you might give it a try just to see. If you get to the end of your project, "reverse stitch" through two or three holes and you are locked in. If your thread breaks, you will need to do this at the break or actually back up a few holes and lock it in with the reverse stitch, then start over.
I so want one of those old singer sewing machines that will sew leather. The problem there is that they are super expensive when you find them. I learned to do my crafting by watching inmates do it at the prison when I was a guard. We had one dude who made something like $30,000 profit one year. He would make stuff for his wife to pick up and take out. She would then sell it and deposit the money in his account. She also took orders and brought them to him. He was good. He made purses, belts, billfolds, handcuff cases, even a few notebooks. He told me once that he had made a couple of handcuff cases for the cop that had busted him. He was good at tooling too. He made his mom a leather carving of the Virgin Mary, and had another guy frame it for her birthday one year. That was a GOOD carving!
I need to find a few different sizes of the Square and Compasses that is the Masonic insignia. Tandy doesn't have the stamp anymore, and I also need a couple that are a good bit larger than a 3-D stamp. I think I can carve it if I can get it in the sizes I need. BTW, that is yet another good looking holster.