I think you can sand down the returnedge at the bottom of your chest a little more, the scews I'm talking about are really small. You can find them in the second picture in this thread, encircled in red.
You can add foam on the inside of your armor wherever you like, as long as it remains invisible. I for example have added foam on my shins and thighs, to make it more comfortable but also to keep the sniper knee from getting stuck inside the thigh, works brilliantly.