Please forgive my butting in but
... I think you should emphasize that middle sentence there where it says "Addon domains will not be functional unless ...
and configured to point to our DNS servers" That has to be done before you do anything in cPanel and some one reading the above might think that they should register the domain first, then go in to cPanel and set up the addon domain and then go to their registrar and set the DNS servers to point to Surpass. But really they have to point the domain to the Surpass DNS servers first, before going in to cPanel and adding the add-on domain.
Because I tried to configure the addon domain in cPanel before I changed the DNS servers with my registrar and it failed for me. I had to do it in the following order...
1. Register a domain name.
2. Configure the DNS servers to be the same DNS servers that I use for my primary Surpass account where I am going to add the addon domain.
3. Then, after the DNS servers were changed with my registrar, go in to cPanel and add the addon domain.