Wonder where the western border would fall out.
The charter calls for "the said lands to extend Westwards, five degrees in longitude, to bee computed from the said Easterne Bounds," which, given that the eastern boundary is a
river, seems impractical to survey.
By my calculations, the northeastern corner (due north of the headwaters of the West Branch Delaware River) would be just east of OTL St. Johnsville, NY; the northwestern corder would be about 6.5 miles north of Dunnville, ON; and the western border would not be so far west as OTL's, barely including central Pittsburgh. (Pittsburgh would be excluded if the western surveyors mapped the border as a single meridian, rather than paralleling the river.)
Now, the charter as written does have an undefined corner: the border is to be drawn from the Twelve-Mile Circle "unto the beginning of the fortieth degree of Northerne Latitude", even though the two circles don't actually intersect.