I found one that my mom got for me for christmas! So i found the jacket in a bag in my living room, and just had to take a peak, and that peak turned to me trying it on, and putting my backpack on, and walking around my house for a little while. Anyway i found that the jacket is fairly roomy in the body, and tight in the chest when you pull your arms back. Now i am by no means a big guy ( i only weigh like 135) but the medium was tight for me in the chest, but roomy around the waist. So if you don't mind the extra bulk around the waist, but want more mobility size up. You can allways get a tailor to adjust the jacket too i guess. But its only 30 bucks. Get 2!!!
Here is a vid. of the jacket, might give you guys a better idea.