I did some research on my Harriss and Diuguid lines and I find that everything I have comes from Ancestry Trees posted by various members of this family.The Diuguid Genforum does post some of the most interesting aspects of the research done on this family.That work is better researched than mine.
I do have Ann Diuguid, daughter of William Diuguid and Ann Moss (daughter of Alexander Moss and Elizabeth Clopton) but none of that data is from my research.Ann Diuguid has plenty of siblings who have all these surnames added to their own names as well as all their children.
Francis Harris marries Ann Diuguid and they have an Elizabeth Harris who marries Luke Ford......that fact is more positively stated by you than anyone else I've encountered. I don't know what documents have this information.
I also noted in the Harris GenForum, when I entered Diuguid in their search engine there were four connections with other Harris - Diuguid marriages during this timeframe.So I am slowly putting this together.