We ordered a new 64GB ssd to boot snow leopard from. And some brackets. Brackets turned out to be useless, as they only allowed for 'side mounting'. But the SSD was so light, that we could _almost_ imagine just plugging it in and letting it hang. But that would not work either. So we took out the mouting bracket from the Mac Pro, removed the four screws that would normally screw into a 3.5 drive, and then used 'zip ties' to hold up the back of the SSD: Seems simple and strong enough. The SATA socket holds the drive in tight, so a loop of zip ties to hold up the back is all that's needed. The picture was taken from the bottom of the case looking up at the drives. One zip tie was not long enough, so we chained two together.