The Duo and Duo 2 have the same pinout. So i needed to have more storage so I pluged my Duo 2 into the Duo Starter Kit.
It the 64G MiniPCIe mSATA card I have installed in the kit.
I followed the directions as follows.
Enter the "Boot Options" menu, go to "Boot device" and you will see two options:
1) D1 Hard drive
2) D2 TF card
Select "D1 Hard drive" and proceed with its prompts.
Select "D2 TF card" to boot OS from a TF card.

This went smooth, but on next reboot i get the following in the terminal at the tail end. and it then just keeps rebooting with the same problem.

Begin: Running /scripts/local-premount ... done.
Gave up waiting for root device. Common problems:
- Boot args (cat /proc/cmdline)
- Check rootdelay= (did the system wait long enough?)
- Check root= (did the system wait for the right device?)
- Missing modules (cat /proc/modules; ls /dev)
ALERT! /dev/sda1 does not exist. Dropping to a shell!
Rebooting automatically due to panic= boot argument