Jock, was it the tiburon top? This was a well known issue that the cut and sew facility sewed the sleeves on wrong and the stretch in the shirt was over the length of the arm, not the width.
I had the same issue, it's pretty piss poor that they won't return it as this was a known issue. But, in some respects I can understand the cut-off date from them. Sucks to hear.
