[libvirt-users] bootloader_args element

I am trying to set the hostname of VMs at boot time and banging my head against the wall. I am using virsh create xen-config.xml to boot a Scientific Linux 5.5 image. I have gone through the libvirt domain xml format at http://libvirt.org/formatdomain.html#elementsResources and I don't see anywhere to set the hostname in there. I am using pygrub for the bootloader and noticed the "bootloader_args" element. Can I pass an argument to the kernel at boot to set the hostname? Can I pass anything to the kernel at boot time? Nothing I have tried seems to work. I have tried sifting through the pygrub code (for lack of documentation) and no luck yet. I think my challenge is with pygrub but any help would be appreciated. I have also posted this at http://lists.xensource.com/archives/html/xen-users/2010-10/msg00143.html and http://www.linuxquestions.org/questions/linux-virtualization-90/setting-h... but still waiting... Cheers, David