I used a 2 GB SD card to back up my dh0: and dh1: on my A4000 last week. Just popped in the sd card and copied the files using DOpus...
On the other hand, I had smaller cards that just weren't recognized. I starting to think these issues are card related but then I've never seen a 16 gb flashdrive! Largest I have is about 512 MB.
Bob