I cut the F-XXX stiffeners on the pilot and passenger seats.
For the stiffeners that are installed at the top of the seats, Vans has you put a .125 inches radius at the vertex of the angle. As should in the image below, i added lines along the length of the angle that define the tangent point of the angle.
I used a combination of the grinding wheel, a file, and sandpaper to get the rounded edge to look correct.
