Question about secondary ISPConfig3 Server

[majstor]

Hi. I want to install ISPConfig 3 Server following the thread How To Run Your Own DNS Servers (Primary And Secondary) With ISPConfig 3 (Debian Squeeze).

My question is this:
Can I make the primary server now (I will add the user for mysql server for the secondary server too) and add the secondary server in couple of months?

Will it be problem to add the secondary server as mirror after I create DNS records, web pages and mails or I must add the mirror server before I start adding things to my ISPConfig3 server?