Jim,
So you are saying that the line of sight crosses the line of bore to an angular extent of .160" over the sight radius. Am I reading that right. If right then you could calculate the angle knowing the sight radius and then check against the ballistic tables.
I haven't shot Black Powder rifles for some time but my foggy memory tells me that for every one hundrea yardds of distance the sight increased by about .100". Again this is highly dependant on SR and my thought are of tang sights with 30 to 32" barrels.
By the way Hi and hope you are doing well.