Welcome to our community, ian.

I have not come across this family before (as far as I can recall) but note a decade old discussion about them here: http://archiver.rootsweb.ancestry.com/th/read/DOUGLASS/2005-03/1112...

I wonder if they got any further?

William

Hi, Ian! Who did you get your DNA testing done with? Look into the Yahoo group for Family Tree DNA's Douglas project.  They should be able to help fit your results in with everyone else's. 

Welcome Ian !

Curious to your line to Phinehas (Phineas) Douglass, I descend from his daughter Lucy Abigail Douglass Gowing.  

For me: Phinehas > Lucy > Abigail "Nabe" Gowing > Hosea Robbins > Frank Robbins > LaMonte Robbins > Ruth Robbins > Me

With http://forebears.io/surnames/ just insert surname at end.
Using http://named.publicprofiler.org/ with Douglas, and Elliot with a single ending letter, they concentrate more on the Scottish side of the border. With Douglass, and Elliott with a double ending last letter they concentrate on the English side of the border, with Elliott highly concentrated in Co. Fermanagh, Ulster, Ireland.

ABOUT "AFRICAN AMERICAN LIVES 2"
"The critically acclaimed PBS broadcasts AFRICAN AMERICAN LIVES (2006) and OPRAH'S ROOTS (2007) shined a national spotlight on the powerful process of discovering one's family history. In February 2008 on PBS, Harvard scholar Henry Louis Gates Jr. will guide an all-new group - poet Maya Angelou, actor Morgan Freeman, theologian Peter Gomes,...."
http://www.pbs.org/about/blogs/news/prof-henry-louis-gates-jr-takes...

Did you know that "Gomes" is a Portugese surname? Peter Gomes of Havard also, and was found to have ancestry that were not slaves, because Quaker, of the Bailey family freed them. Did you know Frederick before he was Douglass was a Bailey?

The precusor to African slaves, in the Barbados Colony origanaly Portugese, then of England, were Scottish, POWs from the Cromwellian Civil War.
http://gorrenberry.com/barbados-pow-scots/

Barbados is Anglican, and the Hamilton were Scottish Anglican, and Alexander was from the West Indies. This means that Alexander Hamilton's family could be from indentured Scots fighting for Charles II. Also means as for us Elliott in America, skin coloration is not a factor, in determining Scottish Y-DNA.

Leaving it up to you, if you think it has prevalence for a new thread, for discussion, and people will be interested in it, I would say put it into a new thread topic for discussion.