Setting up Addon domains and dns

I have some experience in webhosting, dns servers, domain registrations, but I'am newbie to cpanel and whm. What is the best practice to handle prim. and sec. dns servers in whm, and how to handle addon domains? I think I will do: cpanel/whm server hostname: s1.domain.tld (bind or powerdns runing on it) ns1: s1.domain.tld ns2: ns2.domain.tld (another server, auto synchronization with ns1) How can I use these nameservers for a new domain registration? For .hu tld domain registration, I need to add zones to nameservers before the registration process start. (I used whm add a dns zone function.) But if I added zone to nameservers, my cpanel user can't add this domain (after registration and) as a addon domain for his account (because it exist in namesrvers yet). What is the best practice for this? (I don't want to allow "Allow unregistered domains" or "Allow Remote Domain" options for my users.) (Sorry for my english.)