changing ramdisk_blocksize using xml file

Hi, I need to resize my ramdisk blocksize in order to boot the new installed linux. In the xml file under <bootloader>you can add value. For "value" I use: ramdisk_blocksize=1024 which works fine at the lilo prompt. Which further depencies are there or what kind of sysntax should I use for the kernel parameters tag? For any hints I would be happy, Thanx Bernd