Made the cut into the fuselage and slowly connected linkages. When this flap is fully retracted, the lower skin fits nicely under fuselage. I did make the bottom hole cutout a little too large so the lower flap skin doesn't fully cover it. About a 1/4 inch still shows. I'll work on solution to eliminate that.
Some people use nutplate here. This standard locknut works fine and the nut is tricky to start.
Lots of small adjustments needed to get full travel.
Combination of spacer and washers to all free travel.
