Only potential issue I see with it is that you've got two identical drives reading/writing at two different bus speeds. You'll get SATA3 out of the HDD bay but the 2011 only does SATA 2 to the optical bay.
I'd feel fuzzier with two SATA2's personally but I'll caveat my response in that I haven't looked at the ramifications in the difference in the interface speeds in RAID. May be none, but may be a lot.