As I said in my last post, a single window in the roof object behaves correctly, i.e. no twisting, opening in the correct manner. It is specifically adding multiple opening windows to the roof object that causes them to twist once they are exported and imported in the new orientation.

Maybe my scatter of posts caused confusion about that.

Very interesting info there Keet about the naming of the hinge objects. I should take a look at the obj file, because even if I can't move the location of the window after importing, being able to add and open multiple windows would still be a cool effect.