I am searching for my "Down" connection too. I have very little info.
Richard Pilson==born 1750'ish
_(we need another name here)born 1800'ish
John Pilson(in Baltimore Md.father of my grandfather)
John Thomas Pilson(my Grandfather--Baltimore, Md b.1845-1932
(John T had 6 children who lived to maturity
Millard, Charles, Wilford, Christobel, Catherine
and Lottie. My Mother Catherine, the last, died 1977.
Family knowledge starts in County Down, with Richard as first we know of,, a location we cannot locate, On a Royal Land grant at "Wileys(Wylies)Hill Head". We do not know any circumstances of the land grant.
Above mentioned John Pilson was one of four sons, in Baltimore,the others Samuel, Robert, and George.
It has occurred in my thinking, that possibly the name Pilson might have Scottish roots.
Good luck in your search