I have run into an issue w/ RHEL versions 6.5, 6.6, 6.7 & 6.8 regarding the following scenario;

When customizing the default RHEL ISO for additional grub.conf, BOOTX64.conf & isolinux.cfg menu items to assist in facilitating kickstart installations the following methods work;

1. DVD media on 8086 BIOS bootrom code
2. USB media on 8086 BIOS bootrom code
3. iLO/CIMC ISO media on 8086 bootrom code
4. DVD media on uEFI bootrom code
5. iLO/CIMC ISO media on uEFI bootrom code

The one scenario where I cannot load the customized grub.conf and/or BOOTX64.conf menu is when creating a uEFI bootable USB media type from the customized ISO. It does not load the /isolinux/grub.conf menu; instead it is loading the default RHEL grub.conf.

I am not certain where the additional grub.conf file is located to modify. Any help is appreciated.