Nice pics of the original Mayhem. That clarifies something I had been wondering about the shoulder pads, which was, why did the ribbing/padding go all the way to the edges (or nearly all the way) on the original but not on all versions of JAL's. Well, I know that it's different because of measurements and everyone has different measurements. For example, on mine, the ribbing is closer to the collar because of my measurements, and there is no room for them to go further out because of that. But as for the fact that they don't line up (the front and back pieces of the shoulder pads) on the JALs I had always assumed it was to accommodate the shoulder gussets. The original shown here in your pic has shoulder gussets as well, though I imagine the JAL reproduction allows for more mobility. You can also notice in the film that the shoulder bunches up on the shoulder when the arm is lifted. Anyway, the reason the ribbing doesn't go all the way to the edge of the shoulder on the new JALs is because of that ~1 inch shorter back piece of the shoulder. So the reason the original DOES go to all the way to the edge is because the shoulder pieces are flush. Cool.
See this picture:
See on his right shoulder (our left) that it makes kind of a triangle because it is bunched up. I think this is because a) the padding is closer to the arms and possibly b) the shoulders are connected as they appear in your image, rather than how the modern JAL version is. The JAL I have doesn't bunch up like that in as much of an extreme way.
Anyway, this is just speculation based on my intense scrutiny of my own jacket and comparing it to the original. In fact, I got to a point where I told myself I would stop comparing it because it's not perfect. My measurements aren't Brad Pitt's and so some things will never be the same about it. As far as I could tell previous to this image, the jacket is identical in pattern and cut, however this is an interesting observation. The next thing to do would be to ask Jonathan himself. I'll see if I can ask him.
Another interesting thing that these pictures reveal is that the stripes are a little different. I imagine the stripes were not part of the original pattern. They were probably added on afterwards so getting them exactly the same wasn't possible unless Jonathan remembered exactly how they looked. I don't think he started offering these reproductions until years after his work on the film so I imagine he just used pictures to get it how it is. Nobody has ever mentioned this before on any site I have been on so I think for the most part, nobody noticed.
And yet another difference, which is interesting, is the fact that the padding is significantly less bulbous on the original in these pictures. They are flatter. The JAL has actual padding in it and it's very rounded and pronounced. I actually loved that about it and it's one of the main reasons I picked JAL's because most other Mayhem's don't have that much definition to the ribbing. The fact that the padding is more pronounced actually makes the jacket hang on your arms wider. It's less like a straight 90 degree angle down the arm like on Pitt's and it's more rounded looking. I have considered laying something on the jacket for a while to flatten the padding more to achieve that straight angle, which I think looks really good, however I am conflicted on if I want to do that because I don't want to flatten the padding too much since I love how pronounced it is. I wonder if the Mayhem was distressed in certain ways as well. It doesn't look as beat up as the main jacket, but perhaps it was flattened some to lay differently. The one in your pics here looks fairly aged but that could also be the quality of the photos. It seems that JAL's patterns are correct but to get the same look some use/distressing is needed. I wouldn't be surprised to learn it's the same with this jacket.
Can I ask where these pictures are from?