Hmmm, so it doesn't, didn't know that, well, work your way to where I left off in post 5, with the selection active, and go to select->save selection, name it, and press OK. Open the non-antialiased document and press ctrl-a, ctrl-c, and go to back to the mask document, and ctrl-v. Go to select->load selection and select the previous selection from the channel scroll bar, check invert, and press OK. Hit delete. That's it, it should be properly positioned now(making sure that the mask layer isn't visible).