They are also way to baggy in the leg to work anytime in the late 18th century. Breeches in this time period were evolving to be tighter during this entire period that by the turn of the century they looked like they were sprayed on. Simply "connecting the dots" between the knee flap and the waistband on both the front and back pieces will produce a comfortable, but not tight, fit.
My build is pretty average and I found adding a couple inches to the length to the pattern kept the knee from riding up when bending.
If you wish to add pockets, you should narrow the fall about 1 to 1 1/2 inches on each side.
The pattern from Eagle View is the solid line. The dotted lines are the corrections.