Thank you for your detailed reply Igor!
Here's what i'm doing with the diablo image-
./flasher-3.0 -u -F diablo_image.bin
this unpacks the image

I then flash the nokia n800 tablet with the following:

sudo ./flasher-3.0 --enable-rd-mode
sudo ./flasher-3.0 -k zImage -f
sudo ./flasher-3.0 -n initfs.jffs2 -f
sudo ./flasher-3.0 -r rootfs.jffs2 -f -R

I get an error when I try to flash the initfs, everything else transfers fine, but then the n800 won't go past the initial screen

Here is the transfer error:
USB device found at bus 001, device address 013
Found device RX-34, hardware revision 1201
NOLO version 1.1.3

Version of 'sw-release'<no ersion>
Sending initfs image (2233 kB)...
Write failed after 0 bytes
usb_bulk_write:Resource temporarily unavailable

For some reason, I can extract and flash initfs from older kernels, but not diablo.

Perhaps I am doing something wrong?
Ok, I have the oldest known firmware that boots on the n800, can I just update the kernel and rootfs? looks like i need the initfs as well.