I used the method I did with the upper side of the spars and did the lower rivet lines of the spars and the trailing edge of the servo tab. I also fit the servo tab horn. I used the centering ruler to get a center between the inside edges of the hinge bracket. I used that mark and a square to get a square line back to the tab. I used that line to align the horn laterally the the forward edge flush with the lower leading edge of the tab. I am happy with the results.
