Traduciendo paso 7
The big question with this unibody mac Mini: "Can I install a second hard drive myself?" The centimeter and a half of extra space seem to imply so.
There is definitely plenty of room for a second hard drive underneath the first. The only deterrent is the availability of a second, longer SATA hard drive-to-logic board cable.
Let's get the logic board out so we can get a better look.