Are you a guy whos weight fluctuates up and down in size? I had the same issue were I bought a slightly used jacket during the summer and it fit just perfectly! The issue is that during the winter months (and just around Robbie Burns day actually) I actually gain some weight and to my anger and disappointment, the jacket was no longer usable.

Are you also getting a matching vest with the jacket? Correct me if I'm wrong but i think that if you do get a vest then il will be a different fit/size then the jacket itself.