I'm not quite understanding the problem. You say that when you click on the stack, it previews the files, I am assuming you mean in Grid or Fan view, but then you say when you click on a file it doesn't open Finder? Why would it? When you click on a file it launches the file in its default program. Also, what "show in finder" button are you talking about? I only see "show in finder" when you hold down the mouse over the stack itself, not specific files in the stack.