Question about NAS template configuration for first shelf

We've got a customer with (9) 600GB SAS drives and (6) 2TB drives in the first shelf of a VNX5300. They'd like to use the 2TB drives for CIFS and the 600GB drives for iSCSI block. It looks like a RAID6 4+2 is a valid configuration for a NAS template but apparently not in the first shelf in a mixed use case like this.? It looks like I'm going to need to either do a RAID6 6+2 with the 2TB drives or add a 2nd shelf and build the RAID6 4+2 by moving the 2TB drives to their own shelf. Is there any way around this? Are there any other options for modifying the template and not being out of compliance? Thanks.