What do you mean with overloading?
The point I tried to make is that a proper hostname consists of at least three parts. separated with dots. Yours only have two parts. and are interpreted like different domain names. It is just like you are trying to get google.com register itself as DDDNS client at yahoo.com. That is the problem
For a example zone file for a local domain see
http://www.daemonforums.org/showthread.php?t=4073. There I use a local domain called "de.filo" and the hosts have names like
kant.de.filo and
hegel.de.filo