This is my second Proper Cloth shirt; it's been worn and washed for about a year and I think I've got the fit down pretty good.
The only thing I notice, is that there is a little horizontal roll/crease underneath the yoke, that you can see in this photo. Is that something that can be fixed by adjusting for posture or shoulder slope? I don't think it is shoulder slope, because there are no lines along the front (the usual indicator of shoulder slope). But it may be posture, because you can also see that there is a very slight roll behind the collar. I hope it's not shoulder/yoke width or chest width, because I think those measurements are pretty good.