Various replacement procedures are described on NOW site.
I really can’t say which is the best. In similar situation several years ago customer opted for hot standby with 2 disks in RAID4 for root and no spares on one controller, but they were 72GB disks; I guess you would not like to lose 4TB worth of space. If you do not absolutely need large contiguous chunk your suggestion looks reasonable; although I’d rather go for RAID_DP without spares.
Search communities, this question pops up pretty often and there were several long threads about it already.