In theory, FAT32 should allow for drive sizes of up to 8 TiB with 32 KiB clusters, however, the 3 TB Hard Disk Drives inside your WD My Book Studio Edition II have 4k sectors, making a FAT32 partition over 2 TiB unlikely unless you can manually adjust the cluster size per disk on each drive at a time to keep the RAID configuration.
Thread moved to WD External Drives : External Drives for Mac.
Regards,
