UGH that bulge drives me crazy when I wear a binder... my best suggestion is to wear loose shirts. My personal method of dealing with this is a tank top and one of my husband's button down shirts. I wear it open personally, but even then it still hides the awful pit flab.
Edit: I do agree though with wolfduality though, there can be too much, but generally, I think that you'd realize the binder is too small or not good style, etc... If it painfully digs in, then that's a good indicator the binder isn't right for you.