Something that I've noticed for awhile is when your setting up a new MD and it's installing the graphics driver (for example, Nvidia driver) it takes a few minutes to extract all the smaller files of the kernel headers. In the past when I've been in a hurry I'd chroot into the diskless MD's directory and do it from the DCERouter, where it takes a few seconds. Is there any reason why it's not included in the tar? I don't remember seeing it to a dist-upgrade and installing a newer kernel than the one in the tar.
Cheers