As I was cutting the straps on my GG mariposa Plus the other day I realized something. There is a bartack that keeps the straps folded over so that they won't come through the buckle. I think that because of the fact that this is a non-structural seam (if you get what i mean) you should be able to get by with just hand sewing two small little stiches to get the same effect.
Also, if you want to sew them down with a thread-injection machine then choose one of the longest stitch lengths. Save weight.