How to deploy SPS joined to SPP in a DR environment?

Hi guys,

Say a customer has 2 data centers (HQ and DR).  A 3-node SPP can be deployed as 2xSPP in HQ and 1xSPP in DR, this achieves high availability as well as DR failover for SPP.

If SPS needs to be joined and is also required to handle DR failover, what is the best way to deploy SPS in this setup?  Does anyone have any references on how other customers deploy it?