Stotz kind of breaks in after a while but it wont stretch, even if it does kind of give in it wont be noticeable. My J1B-S feels a lot different after ~2 years of wear and lost the kind of stiffness it had when I got it. The J36 will also soften up a bit, but it takes some time.
About the cuffs, it depends how tight you really want it. If you tighten it normally and fold the material at the beginning of the velco it will be just right. But I'm afraid there isnt a good way to tighten it even more without the velcro sticking out.