Decommission primary hub server - considerations?

We’re looking at decommissioning our primary hub server, due to various reasons.I have set up another domino server, clustered the two together, and replicated all the databases.

Once I have set up connection documents to the other servers, is there anything else that I need to consider?

Something the primary server does that no other server in the domain can do?

I know about the SMTP considerations, hostnames and such.

Subject: decomission server

Make sure that you cross certify the server with othe doomains or servers

Subject: How do I do that?

How do I cross certify the server? I cant find anything about that in the Administrator help file.