you can't have active-active setup with CSM.
The CSM uses only 1 FT group and all vservers are linked to it.
So once CSM is active and the other one standby.
If the FT group fails on the active, the standby takes over and it takes a full control - not partial as needed for active-active.
It does not matter if you have 1 chassis or more.
The new ACE module offers the possibility to do active-active.
Gilles.