Through the help of researcher Michael Ruddy, I have learned that Elijah Hadsell (born April 10, 1759 in Rhode Island; Revolutionary War Veteran; married 1795 Anna Michel in Berkshire County, Massachusetts, and moved (before the 1810 census) to Cobleskill, Schoharie County, New York) was NOT the son of William and Dorcas.
In addition, the Isaac Hadsell born in 1770, and who married Isabel Eldred in Berkshire County, MA in 1794 (?)was actually a GRANDson of William and Dorcas, NOT a son (Isaac was the son of Joseph and Thankful (Newton) Hadsell).
I still believe, however, that there are three more children of William and Dorcas who are waiting to be discovered (the first seven children are indeed taken from the Rhode Island Vital Records, as published by Arnold).My belief is that William and Dorcas might have moved slightly West, across the river and into Stonington, New London County, Connecticut about 1758/1759 and these three last children might have been born there (and so are not in the Rhode Island Vitals).
So I am still searching for a possible daughter Elizabeth Hadsell, born ca. 1760, who could have married Nathan Whitford in Berkshire.