ME4 Tier Question

Hey guys, I have a query which I'm struggling to get an answer for from docs or sizing tools.

Imagine I have the following configuration, I know that two disk types is recommended, just go with it.

24 x SSD in the head unit
12 x SAS in an expansion unit
12 x SATA in an expansion unit

I then provision two virtual pools and want ADAPT. I'd end up with the following as you need 12 drives for adapt. I assume when I create a volume in poo1 it will tier, and if I create one in pool2, it will not. Is this correct? I presume I'd need to end up having RAID 5/6 groups instead and split them across the pool, from what I read tiering is done per volume and the volume ultimately lives in a pool.... I presume the volume on pool2 cannot tier to pool1 as its ultimately on the other controller.

Pool1
12 x SSD ADAPT
12 x SAS ADAPT
12 x SATA ADAPT

Pool2
12 x SSD ADAPT