I'd love to see what you have. I know of the Rev. James Duff that you speak of. My 6th Great Grandfather was Rev. Robert Duff, son of Robert Duff of Hillockhead. His son (my 5th ggrandfather William Duff of Foveran) was also a minister, as well as his other son Patrick (of Old Aberdeen.)
Rev. James was just the generation after my Rev. William.
Being from the Hillockhead Duffs, we're related nicely down the ladder from Adam of Clunybeg.