Does anyone know about rear storage solutions for the iMac? The two I know of are the twelve south backpack and the Just Mobile AluRack. What I want to do is afix an external SSD to my iMac. Since it will be my boot drive I am concerned that it would be basically 'one' with the iMac. Of course this would be resolved if we could add two 3.5 drives internally but since that option was taken away from us, well ... The Backpack seems not as solid as I want. Plus the drive would get detached the times I need to move my system to work elsewhere (and when that happens I do not have time to grab multiple things). The alurack is more promising as it screws directly into the hole on the back. All the pics show it holding laptops though so I am a bit dubious if it would hold whatever drive I buy. Any options I am missing?