Chosen Solution
I am aware that opening this iMac is difficult. As it is still in warranty, I don’t plan to do anything at this point, but I wanted an answer to the following question (My iMac currently has a 500 GB SSD only). If I were to open the iMac, would it be possible to mount either an aftermarket SSD or a standard HD in the place where Apple would have installed a Fusion Drive? Having looked at the iFixit tear down of the iMac to replace a SSD, I think mounting one where the HD could have gone would be far simpler. Thank you in advance for any information you might have.
Lets quickly review what a Fusion Drive is: It is the marriage (fused) of two devices, a traditional HD and a SSD to be seen within the OS as if it was one drive (logically one drive). So if I understand what you bought you got the 512 GB SSD model (blade drive using a PCIe 2.0 x4 NVMexpress interface]. So the SATA port connection is currently unused. So you can add a second drive to your system either a 3.5" HD or a SSD with a 2.5" to 3.5" adapter frame. Only the HD can be used in conjunction with your current SSD to create a Fusion Drive. Dual SSD configs can’t be made into a Fusion Drive set. You will need a drive cable and you’ll need a special in-line thermal sensor made by OWC.
