Unable to install Windows 10 to a Z170X-UD5 with M.2 RAID configured

[Skysis]

I have a Z170X-UD5 (open box from Newegg) with an i7 6700K, Corsair Vengeance LPX (2x8GB), and 2x Intel 600p M.2 SSD's (all new). I have RAID 1 configured for the two M.2 SSD's. The SATA option in BIOS is RAID. I'm trying to install Windows 10 Pro 64-bit on the RAID volume - using a USB drive created w/Rufus from a Microsoft ISO file. I can get as far as the installation of additional drivers where I tried installing Intel's latest RST drivers. I downloaded them from both the Gigabyte site and the Intel site. It's the same version but with different dates it seems. The drivers load, but no volume is seen, and I'm stuck being asked to load more drivers. I tried the process several times, sometimes the drivers take several minutes to load, sometimes seconds. Installation to a single M.2 SSD with AHCI setting in BIOS is flawless. Not sure what else I can do. I would greatly appreciate any suggestions.