This video is extremely helpful when it comes to fixing Hisss' reversed shoulders:

http://www.youtube.com/watch?v=KyVNh...layer_embedded

I am not sure if it's necessary to cut the armor as he did as the other pictorial tutorial shows that you can slip the armor out if you heat it up. On the other hand, he has shown us that it's not at all necessary to mod the figure in any way as you can indeed remove the shoulder from the joints. This allowes you to reverse them without having to open up the torso and sand off pieces to swap sides.