I'm contemplating ordering an MTM shirt. To specify the sizing of the shirt, I plan to send in my best-fitting shirt and tweak the measurements slightly. Here's my predicament -- I have several shirts which have almost identical measurements, but each fits differently. In fact, I have two shirts purchased at the same time from the same manufacturer in the same size. One shirt fits much looser than the other, yet their measurements are identical. So, the only thing I can conclude is that the fabric of a shirt factors into how a shirt fits. Is this correct? If so, how can one specify measurements for an MTM shirt and expect the correct fit if the fit is dependent on the fabric?