yes, them Robart Hinge Points are a Headache. I usually find the Center with Calipers, drill a 1/16 Hole and open it up to .156 with first a 1/8 and then a 5/32 Drill. Then I stick a 5/32 Rod in the Hole and measure again, from the Top of the Trailing Edge and the Bottom. Finally I finish to .187 with a Rasp or course File and adjust for inaccuracy's of the location. I do the same procedure with the control surfaces. Yes it's a Pain in the Butt but it works for me.