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There are three screws that are longer than the rest. Maybe you are trying to put them in the wrong spots?

There is a picture at this link...you might have to refresh if it doesn't show the first time.

http://support.apple.com/kb/ht1270#link1

Used that chart on my iPad... I'll leave it for now. If I continue I'll need new screws. I placed each screw back into the location they were removed. All the long screws are positioned fine.
 
Turn counter-clockwise slowly until you feel the head seat, then drive me home clockwise.

If you look at the cover you can see that the front lip tucks back a little.

Thanks. I managed to get two of the screws to sit a little better. One screw is slightly out, but I can live with that for now.
 
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