I also just got my binder from Underworks, the 997. and I am having this problem as well. Only it's not just cutting into my arms, it's cutting into me at the end of the shirt (at my hips), and it's kind of gathering in my middle at my upper waist, and it's cutting into me there too. I actually wrapped a scarf around my upper waist and then put the binder on top of that, and that felt a LOT better. But it didn't help with the cutting into the hips or the armpit area. I'm thinking I should try putting some padding in those areas until I (hopefully) stretch out the binder a little and it doesn't do that anymore.