Use fanoush kernel_flasher is much much easier.

http://www.wahlau.org/updating_n800_..._different_way

But is there a better way to update the kernel on the MMC instead of on flash?

More info:

- kernel_flasher runs on N800 so you don't need a pc!
- just download *deb kernel-RX* file to a directory you choose
- kernel_flasher does not need any option on the command line (-k -f )