Alienware 17 R4 Windows 10 and Ubuntu dual boot?

I recently got a 17 R4 with gf 1070, 512GB nvme boot drive + 1TB HDD and I'm on a quest to dual boot the factory Windows 10 and Ubuntu 16.04LTS desktop. I added a Samsung 512GB nvme ssd to act as the drive for the Ubuntu installation, while preserving the original nvme drive as Windows 10 (the 1TB hdd acts as a data drive...no plans for OS there). The relevant default bios settings are UEFI boot with Secure Boot enabled and drive subsystem set to RAID.

Now, from experimentation, it's apparent Ubuntu installer can not see the nvme drives when the bios is set to RAID. This was expected and setting it to AHCI resolved that problem, however, when trying to boot back into Win10, it refuses to boot with the "INACCESSIBLE BOOT DEVICE" error.

So, as my first hurdle, how do I get Windows 10 to boot when bios is set to AHCI?

THX