First I'd like to acknowledge the FAY research you have done on the line of David thru Frank E that is posted on your website. It proves to be quite helpful to tie theline in question to the immigrant father John FAY of Marlboro, MA.
Second...I'd like to add the line of Frank E Fay and Mary Carr / Catherine from McHenry County, IL has a branch that migrated to CA. Additionally photos were taken of the gravesite of Frank E Fay buried at Ringwood, McHenry County, IL as well as that of Frank G Fay at Alden, McHenry County, IL. It is confirmed - as you suggest - these are two separate FAY lines. If you would like to add the photos to your website, I would be happy to provide them for you. Photos of Simons, Spaulding and Ritter are also taken.
The line of Frank E Fay/Frank E Fay/Daniel Rodger Fay migrated to San Francisco; living descendants reside in Redwood City, CA. Frank E Fay (Jr) was born 1935 and died only a few years ago. The family did not realize they descended from John Fay of Marlborough and thought they were Irish. If there are descendants from Daniel's siblings - Philip and James - I would enjoy sharing information.