No Problem, just wanted a faster mac mini.
Fine, HDD was a close fit (Corsair Force 3 120 GB 95mm). I had some trouble getting it al in. (3d puzzle in a partly closed box).
If it does not exactly fit, try again. (unless the height of your HD exceeds the max measurements).
Some details about the install when reassembling:
1. When possible, see to it the HD connectors are above their connections, but do not connect them untill everything is in it's place. (You should double check anyway if all cables are correctly connected).
2. The power suply cables should go below/above the Hd's as much as possible.