I used a metallic pleather for this bag before I attempted to try it with real leather. I had some issues. I have never had to sew around D-rings, sew this type of material. I used 44" for the strap instead to make it longer. One thing I did note is that the instructions do not tell you to sew the 13" or 14" side when you are sewing the two outside sides together.
I don't love this bag right now. I think I might prefer it in a much flopper material. Probably a soft leather would be nice. :) Also, I think it's a tad too big. But it certainly was a learning lesson!