If going to cluster mode is an option, then reinitializing the system on 8.3 or later with advanced drive partitioning would be ideal.
If you need to stay on 7mode, which may be the case since these are for functional testing and likely need to match the client configuration/ONTAP release as much as possible, then you've got a few choices:
Active/Idle with shared root aggregate
Active/Idle with dedicated root aggregate
Active/Active with shared root aggregate
Active/Active with dedicated root aggregate
Shared root aggregates are not ideal, but it was a common compromise on entry level 7mode platforms.
Active/Idle configurations give you a single larger pool of capacity and performance.
It comes down to what your priorities are and how you intend to use the systems.
