I'm having a hard time figuring out how to use stacks. If I export a group of photos to photomatix, which then exports them back to LR and stacks it with the original, I can see that there are two pics in the stack, but cannot view the second one. The only way I can is by choosing the second display icon, but I can't figure out how to see it for development. I've tried expanding the stack, but nothing seems to happen.