I haven't seen any of the newsletter issues since 2011. I can tell you that the ancestral lineage given for Deacon John Dunham in Isaac Watson Dunham's book Dunham Genealogy IS wrong/partially fictitious. So do not take anything in that book as fact unless you prove it with records yourself. (That can be said of the majority of unsourced family history books.)
The American Genealogist (TAG) has several articles on Deacon Dunham one of which is the first report of finding Deacon John's first marriage and baptism/christening of his first son. Bedfordshire and areas nearby are not as well microfilmed as other areas of England so digging into the records there requires more effort.
I know there was talk of researching Richard Dunham of Langford further than what was in the TAG article but I do not know if anything developed further than talk.