I can confirm that using 575-BBSP will allow you to setup two NVME drives in a Raid 1 with a MegaRaid 9460-16i and boot from it.  If you already have flex bays all you really need is the cable.  The cable is part number 04MMDF (at least that's what is marked on the cable) but no one at Dell has been able to find that part.    I hope this saves someone else some time.  
I have a T7920 and I am trying to upgrade the boot drives to 2TB NVME drives in a Raid 1.  I have added the flex bays, the NVME backplane, the NVME drives and caddies and a Dell MegaRaid 9460-16i card.  The issue: The Raid card will not recognize the nvme drives.  Here's what I have done to trouble shoot: This looks like something to do with the MegaRaid card but I can’t find any info on what I’m missing.  The system is out of warranty and Dell doesn’t offer support on specific cards (the megaraid was purchased new from a third party).   Anyone have any ideas?  Thanks in advance for any help.
Precision T7920 M.2 PCIe SSD (NVMe) Drive not Detected on MegaRAID 9460-16i 
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