When I had a case with what I believe are similar mounting pieces and my Vantec Nexus, I was going to cut two strips of metal (or anything.. popsicle stick?) and glue or screw or attach however the strip down to where the screws would need to be..
Then drill a hole where the hole you need would be, and mount like normal... might not be the most super sturdy method, but at least it gets it in there...
Although the Nexus may be too different (but I dont think so) or the case might not mount in the same way (possible)
Does the CM Stacker have the drive bays where you must punch out a piece to slide a drive through? If so, does it have a piece that you can fold back to make a shelf? If so, maybe some double sided tape sticking the SunBeam down onto that shelf?