That was trial and error, but next time I might run two stitches in the middle and leave about 1/8" space in between. It works but they are really close to each other.
I think one can also do a triple pouch that way. My next project gonna be a double pouch based on your P938 pouch for my wife's P239 .40 which got also single stack mags. Just need to get me a little drill press first so I can drill the holes for the stitching with a 1/16" bit and get the sanding and burnishing done nicer.
Still learning as I go. Made my first pattern for a dual position holster for my P229 also which allows me to carry either cross draw or strong side. Will see how that comes out.