STAS - multiple collectors & agents?

The setup:

2 sites with 2x domain controllers each (for resilience)

Do we:

1. Put STAS collector/agent on one site dc and have 3x agents on other dcs

OR:

2. Put STAS collector/agent on all dc's

OR

3. Put STAS collector/agent on both site dc's and agent on other dc's

Looking at the above:

Option 1 = if dc with collector goes down, it fails to work

Option 2 = completely resilient although Sophos doesn't say whether this is acceptable eg 4x collectors/agents

Option3 = Not as resilient as option 2 but works with principle of collectors/agents & agents