Add Physical Disks to RAID 1 Virtual Disk on H730P?

Is it possible to add 2 more physical disks to a RAID 1 array (new disks identical to the old disks) on an H730P without destroying the original mirror? OMSA isn't showing an option to keep the original RAID type when I do a Reconfigure in the software, but is it maybe possible in the controller BIOS? And without destroying and rebuilding? I would reboot and check myself, but it's a heavy production server and I don't want to ask for a maintenance window to reboot it just to go poking around unless I've got a pretty good idea of what is or isn't possible beforehand. Thanks in advance!