Hello Ken,
I think I understand from your previous posts that this is not your line, but in your local delvings, would you have come across any of the Stewarts who settled in your area in the mid-18th century? Seeing your location, I couldn't resist asking
One of my biggest Scottish brick walls is Edward Hill Stewart, who was married in 1782 in Frederick County, Maryland. He was born around 1759-60. Stories conflict about whether he was born in Maryland, or came from Scotland as a small child (but I can't find any convincing record of his birth in Scotland).
Two of his children lived past 1880 and both report in the census that their father was born in Maryland (the family went to Ohio around 1810). A family tree, made by a descendant in 1917, says he was born in Edinburgh. This may be telescoping generations-- perhaps his father or grandfather came from Edinburgh, but in order to try to take the family back, I need to find the name of Edward Hill Stewart's parents...

I have transcribed all the Stewart wills from the county, with no luck. There is an "insane" Benjamin Stewart, a Posey Stewart, an Alexander Stewart and a few others, but none with a proven connection to my ancestor.
I know this is a stretch... but since you live in the area you might have some idea of what sorts of records are available for that time period and if there is something obvious I have missed.
All the best,
Sarah