[CentOS] Installing from USB

I found this http://wiki.centos.org/HowTos/InstallFromUSBkey

So for centos 7 if did the dd command seemed to work great.
I did the install.

So now I'd like to "modify" the USB key to add a boot menu option with my
customer install options. I mounted /dev/sdb2 and edited the file
/mnt/usb/EFI/BOOT/grub.conf

added my menu item and rebooted to try to use it.
It does not show up in the menu.

How do I get the USB to use my new menu?

Thanks

Jerry