9/3/2016 Update: I reworked the frames and mounting bracket. There is more space between the parts, so they should fit together easier. I put the larger cutouts all on the same side, so it should print cleaner. And, I fixed a few of the screw-holes.
One 3 hole and two 9 hole frames will Cover the back of the Mini.
I used 12mm m3 bolts to secure my Pi to the mount. 10mm with standard nuts might work, too. The screws are 3/4inch #4.
For front mounting I use this: https://www.thingiverse.com/thing:1764077