Works for me as well! Based on your instructions.
Question:
From the EFI shell started from DUET, how do you chainload Windows 8?
I cannot access the Windows 8 install HDD or the Windows 8 setup USB.
There is only fs0: which is the DUET USB.
I guess exiting the EFI shell and starting Windows 8 from the DUET boot manager will reset the adjustments done in the EFI shell?