After conversion from single drive to a 2 drive RAID 0, new RAID volume size is the size of one of the drives

Got a weird one...

I had a single 6TB drive that I wanted to put into a RAID 0 volume with another identical 6TB drive.  I created the volume using RST, preserved the data off of the correct drive, and waited ~3 days for RST to copy whatever data it needed to from one drive to another.  Now that the copy is complete, the new RAID 0 volume only shows up as 6TB in Windows, even after a disk rescan/warm boot/cold boot.  Shouldn't the new RAID 0 volume show up as 12TB to the OS?  When I look in RST, it does in fact show a RAID 0 volume that's 11,178GB so why doesn't Windows see that same volume?

For reference, I'm using the following:

Intel DZ87KLT-75K motherboard

Drives in question are two HGST 6TB 7200rpm SATA 3 3.5" hard drives

Windows 10 x64 in UEFI mode w/ Secureboot

Intel RST v14.6.0.1029

RAID Controller Driver v14.6.0.1029 (dated 7/27/2015)

Thanks in advance!