Move registered Forticlients to another Fortigate

I have over 200 Forticlients registered to one of our Fortigate clusters. The cluster involved is about to be decommisioned so i need to re-register our clients onto another Fortigate cluster.

Currently our users are using the 5.4.0 Forticlient package rolled out through MS SCCM, and are registered to a Fortigate 800C cluster running FortiOS 5.2.3 The new cluster i need to register them to is a Fortigate 100D cluster running FortiOS 5.2.7. Both have ample Forticlient licenses activated on them.

The new cluster is configured with the same forticlient profile settings etc.

I am trying to figure out the easiest way to have the clients register themselves on the new cluster without any interaction needed from the users side ???

Any ideas ???