i did the same i have the 60gb with B/C stored it away and bought a 120gb in June i replaced the 120gb with 320gb 7200rpm HDD
the DT transfers the copy righted saves but once you go back to the phats save data all the copy righted saves are gone they only can move from one system to another 
so thers no way to store those saves in case something happens to the slim
i deleted most of my non used stuff demos, game installs, ect so my DT took only 23mins

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