Logical layout of Equallogic storage pools with new members

In each of our server rooms we currently have 2 Equallogic storage pools:

- 10K-1GB (2 X 6100X)

- 7K-1GB (2 X 6100E)

We have just purchased an extra PS6100E and a PS6100XS for each server room.

The existing 6100E arrays that we have include 3tb disks and the new one includes 4tb disks. These arrays don't usually have much load placed upon them and are mostly used for mapping network shares or backups / replicas. Can anyone perceive an issue with adding the 4tb 6100E's to this group ?

I was planning on deploying the 6100XS in its own pool, as the advice I read was not to mix it with other array types.

I'm struggling to remember now, but can you specify a different pool to join a new group member to or does it always go in the default pool first ?

If it always goes to the default pool first, is there a way of changing a new pool to become the default pool ?

Thanks