I didn't realize your controller wasn't set to Raid from the get go here, nor did I ask so that's my fault. I don't actually know why people use ahci vs raid even if you aren't technically using a raid set, but I assume there is some reason. I searched for a bit about switching from ahci to raid with this controller, but unfortunately found very little on it.
It looks like there are two different pre-install drivers for this chipset, one for ahci, one for raid. I don't know how/if it's possible to get the Raid one into Windows post install.
Bottom line you can definitely run this setup, but you may need to reinstall windows with the controller in Raid mode. It's very likely there is another solution to this, I just can't seem to find it.