After reading these excellent instructions I wanted to try the same. However, I don't have a dremel tool. I wanted to use my miter saw but was stumped for a while about how to hold the adapter in place during the cut. I ended up masking off the part of the board with the connector and using some #4 machine screws in existing holes in the board to hold it onto a piece of 2x6. This kept my guide hand a safe distance away from the cutting blade, but I had to take care that I wasn't cutting next to one of the machine screws. I also swapped my normal 60 tooth finishing blade for a 200 tooth plywood/osb blade. It worked quite well, but as has already been noted PCB is surprisingly tough stuff. I'm glad I went with a fine toothed blade and took my time during the cut.
Here is what it looked like after I made the cut:
Here is what it looked like after I installed the adapter with a drive in my PBP, but before I added a 1.5 mm thick strip of thermal pad between the drive and the bottom of the case:
Here is what it looked like after I made the cut:
Here is what it looked like after I installed the adapter with a drive in my PBP, but before I added a 1.5 mm thick strip of thermal pad between the drive and the bottom of the case: