I do wonder sometimes, if, with some fabric glue and a lot of patience, you could get the poncho into the exact position it was in the film. All of the patterns are accurate and everything, so, there should really be no reason why you shouldn't.
I think with glue and patience you could get it damn close.
Straight pins underneath work too. Not as permanent as glue.
I've used those little tiny magnets you can get on e-bay on other older ponchos. I would not use glue on a an expensive piece of art like this, plus you may want to change poses and styles one day