The Specs do not show that setup to be supported. They only show 256GB SSD or 1.13TB Fusion.
It may be possible for it to see the 756GB SSD as a single drive but it could be an expensive experiment. Also the Fusion Management doesn't support 3TB, see here:
Sorry that link doesn't adderss upper limits of Fusion size but I know I saw it somewhere.
The new version of Disk Utility won't properly address an internal SSD and HD.
The Fusion in the iMac is undoubtably a 3.5" HD paired with a SSD. The MacMini can only accomodate 2.5" drives.
Joe, the 1.13 TB Fusion is a 128GB SSD not the 256GB.
The 10.8.2 build (12C2034) that shipped with my late 2012 MacMini created a fully functional 1.24TB Fusion drive after I ran Internet Recovery Disk Utility on each drive. They are now merged into a "logical drive" and seen as a single volume.
In all the articles I've read NOone has actually allowed DU to do the "Repair", many have noted the error messages, OWC has a work around so the drives aren't seen the same way. Every article has either tried to create their own Fusion or figure out a way to disguise the drives.
No one lists the Link/Negotiated Speeds of the Apple Fusion. Mine are 6G for the SSD and 3G for the HD, System Report still identifies the individual drives.
There is no point in having a really big SSD because the Fusion File Management System built into the newest iteration of the OS will keep what it wants where it wants it, no choices for you. You can also only have 1 additional partition under the DU for Fusion, a really big setup .756/3TB Fusion would be waste, you would be much better served by a ThunderBolt external hard drive or RAID setup.