With this config (assuming a "load balance" HA Setup) you are not facing the raidgroup size question...
two controllers / each with one aggr0 of 11 disks, leaving 1 spare disk per controller...
Peter
PS default raidgroup size with SAS disks is 16 disks per RG (max 28)
  
RAID-DP (Default)
ATA/BSAS/SATA: 14     FC/SAS: 16     SSD: 23
(Maximum)
ATA/BSAS/SATA: 20     FC/SAS: 28     SSD: 28
RAID4 (default)
ATA/BSAS/SATA: 7     FC/SAS/SSD: 8     
(Maximum)
ATA/BSAS/SATA: 7     FC/SAS/SSD: 14