On the topic of physical location of an added SSD... Somewhere I read Upon adding an SSD to a Mini, the OEM HDD should be moved from the lower slot to the upper, and then the aftermarket SSD mounted in the lower slot. Not sure if it was because a few upgraders had problems that were fixed by this location swap or if it was to get some performance advantage. My new to me 2.6 MM has the added 512 840 Pro SSD in the upper (was empty) slot. Is this smoke and mirrors, or is there a good reason to move the primary drive to OEM's single drive location? How does Apple orient the drives for the OEM fusion set ups?