Personally would not be happy with that kind of error, especially not at IH prices. I have a fair amount of IH pieces and they are wonderful, but the prices are only justified by their longevity and precision. Is the difference only in where the sleeve seam meets the yoke, or is the yoke itself crooked?
With that specific difference i woudn't be surprised if the underarm piece slipped in from a stack of cut pieces from a higher grading. When I ordered the last large 526PJ from Rivet and Hide a year or so ago they told me the it was actually a little larger than the general allowance, but it fits great and its kind of fun to have an oddball.
That's a great idea! And, I can assure you - it's a beautiful jacket. The only concern I have with lined jackets is that the materials behave differently when washed. Have you ever had an issue with that?
