What do you mean by retrofitting code, pYro_65?
'borrowing' then converting to my needs.
I've been looking at some examples of mass storage. The library provided with the due has a full CDC layer. On my day off I'll start to implement subclass 01h/50h with the newer 'Bulk-Only Transport', which would be fine with all flash drives and most external HDD cases ( no cd/dvd, floppys, tapes ).
It looks challenging, but definitely doable.