I recently installed initfs flasher on my n810 and I was able to get it working and boot from the internal media card.
I could only get it to work with version 1.2007.42-18 or 2008OS, I had upgraded to .42-19 but I was not able to get it working until I downgraded back to .42-18.
Also when the boot menu comes up none of the keys on the n810 work so it just boots to what I have set as default (mmc2, partition 2) after the 30 secs or so count down.
chroot /mnt/initfs evkey -u -t 5000 /dev/input/event2