Maybe you should try contacting WD’s Technical Support about this (you can do so either by phone or email). As far as I understand it, you can NOT upgrade those drives with larger drives, or do what you are attempting to do.
I would like to know too if anyone was able to update a My Book Studio II with larger drives.
I contacted support and they told me you can only change a drive with one of the same capacity but I wanted to check here too.
Certainly it’s a bummer cause I was convinced when I bought the drive that you could upgrade the system with larger drives and apparently I was not the only one.
I don’t understand what prevents larger drives to work.