I completed this guide last night on my iMac and it all worked great until I got to step 26 and none of the holes on the 12.7 mm PATA Optical Bay SATA Hard Drive Enclosure lined up with the black plastic faceplate. Just like what is being commented on by previous fixers, I could only get 2 screws on one side of the enclosure in, but they were crooked and unable to screw in all the way. It was crude, but it worked.
The rest of this guide works flawlessly. This is a great site!