I don’t know if I’m the right person to ask this to either, to be honest :3
but anyway, from the point of view of someone who doesn’t know anything about costumes I’d say it’s a pretty faithful adaptation?
It’s obviously not an exact replica, and I don’t think an exact replica would ever actually work on stage but if you compare it to other versions of the coronation dress I think it’s safe to say this one is one of the closest to the ‘original’ [not that there’s anything wrong with having different costumes, of course]. Despite the lack of veil [is that even the right word for it?] and the fact that the skirt is much shorter [for obvious reasons] the bodice is very close to the original and so is the general cut of the dress. And even the embroideries on the skirt follow a similar pattern to the one Sissi wore