Adding MSA1500CS to cluster w/ MSA1000

[CG_2]

I have two DL580s in a Win03 cluster, each with two FC connected to a MSA1000 running the active/active firmware. The MSA has two of the 2/8 switches installed. The FC connections from each of the DLs go to both switches. At this moment my setup is without any single points of failure.

I'm looking to add more clustered storage and can tolerate even slower disk. I know I can add up to 2 MSA30s to the MSA1000, but I may need to scale much higher.

Will I gain any single points of failure if I do the following?
1. Connect a MSA1500CS with two controllers and two FC interfaces to the switches in the MSA1000.
2. Connect MSA20s in pairs to the MSA1500CS and make RAID1 arrays that span the pairs of 20s.

If I pretend that a SCSI cable cannot ever fail, could I use one MSA20 at a time and be RAID5/6?