Thank you for your comment John. I too am quite cynical. That is actually a very good trait to have when doing genealogy. I have been cautious when examining the work of David Boles. I would be skeptical if he had put together just one book on his own family history, and was vague with his sources. Ideally, one wants to have official, legal documents, but going back to to the 17th and 18th centuries it isn't always possible. I have found him to be cautious when making assumptions in some of the other families he has researched. His link I posted to Dugal McQueen's profile does not list sources or go into details. He saves that for his Boles and Barth Ancestry Omnibus book, which I have in my possession. His body of work extends way beyond Dugal McQueen and his own personal family. He has also published books on many other families including hundreds of names from immigrants, colonists, and pioneers, and has been publishing since 1986.
Compared to what is already listed as sources for Dugal McQueen's parents on WikiTree, which is sparse at best, and mostly Gedcom imports from Ancestry, I found this to be more informative.