By stitching the strap to the gusset the way you did you stopped the gusset from expanding. So if you look at what you did, then your original design issue could have been resolved by making the gusset less wide at the top. The body type of the individual for example if they were big would still pull the gusset away from the bag also. Whatever goes in the gusset pocket if heavy would also pull the gusset outward too. Overall, it’s a great, useful messenger bag, I like it.