You can't mix NetApp disk in aggregates with 3rd party disk... so it comes down to the same sizing you would do on any NetApp controller. Usable disk and performance... 12 or 24 depends if it meets your IOP and MB requirement and space.
Also, when using NetApp shelves on v-series... we set an environment variable on ports used for netapp shelves... for example, setenv fc-non-array-adapter-list "0b,0d" if 0b and 0d are connecting to shelves. We don't have to do this with 8.1 but likely you are on 7.3 or 8.0 and rc1 code.