Fit question on schott p631 buffalo leather jacket

[Aloysius]

425 dollars for a USA made Schott with a fur collar is a STEAL.
The Schott shoulders are narrower by design in my experience. But they should still work. Most slim cuts patterns are shaped this way.
The torso can use a pair of gusset cinches used on the half belts. That will solve your new jacket fit issue. These sur coats are really cool. I love them. Once they break in the back will look a lot nicer. The longer the jacket the worse it will look (fit wise) when new, but in time it will get better.
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Yeah it's worth noting as well that the heavy weight leather Schott's fit considerably closer after break in, once the big panels aren't pulling away from your body like boards. A 3/4 car coat like this isn't going to be rider-snug, but it'll be a nice trim fit that suits the kind of jacket it is.