You should be able to register a 6.5.3 SP2 Agent after you have applied the LU4201 as stated in the CCS 11 Planning and Deploymnet guide. This LU (it is not a full SU) only has the Agent Information Module and it will give CCS 11 the information required for it to recognize the agent. No other Agent modules are updated from what I understand. Once this LU is applied, then a new policy named Agent Information (or something like that) will be available and will need to be run to pull the necessary information about the Agent such as OS, versiont, etc.