I have some info on Flossie's branches of the tree. Flossie's parents were Freeman C. Nickerson (1870-1929) and Mary Elizabeth Brannen (1872-1962). Her maternal grandparents were Jeremiah B. Brannen (1833-1904) and Mary Elizabeth McGray (1843-1933). I can go back 11 more generations on that branch to First nations peoples in Cape Cod if you want. This tree also incl. Pres. George W. Bush.
If you would like to exchange info, just EM me here or at my personal EM address (posted w/this message).
I would also like to suggest that you contact the "Nickerson Family Association" in Chatham, MASS. They have a few mountains of info, a small portion of which I was able to tap into.