I'm refitting a mid 2011 mini. Reinstalling the drive easy with a few tricks:
*Step 11.5: add registration marks to the thin plastic drive cover.
**Use a fine point blue sharpie (or similar).
**Add two lines a couple inches apart, extending back from the metal housing lip onto the drive shroud.
**Add two short lines by tracing the curve of the housing across the first two lines.
**Use the marks to line everything up when reassembling.
*Reinstall with the mini standing on it's front end
**The drive slots in high in the case. There is a substantial gap between it and a 9.5mm second drive. This makes it hard to line up with the mac flat on the table.
*You can absolutely feel the drive's pegs engage into the rubber mounts.
*When seated properly:
**The drive slants slightly down from the front to the back of the housing.
**There is a sizable gap (~2mm) between the visible long edge of the drive and the flange on the plastic frame that sits behind it.
**The motherboard will seat ~1mm from the drive.
Look at all of the images. Initially, I took the text literally. I pulled the tool straight back without letting it pivot, and without success. I suggest the following additions: "The tool acts as a lever. Carefully pull the top of the tool down and toward the I/O board. The logic board and I/O board assembly should slightly slide out of the outer case."