[CentOS] installing updates in post kickstart

I can do a yum update in my post kickstart (which is what I am doing now 
actually).

However, I want to save network time at installations.
If I copy down the files from centos/5.3/updates/x86_64/RPMS
and place them in a directory local on my network,
can I just "rpm -U /mnt/directory/updates/x86_64/RPMS*"
in my post section?

Assuming I have nfs mounted the directory of course...

Thanks,

Jerry