I used the stiffener that was drilled to the seat back as the drill jig for the remaining 3 stiffeners. All the holes were drilled to #40 size. I’ll open them up to #30 when they are match drilled to the seats.
I drilled the left stiffener to the pilot’s seat. I drilled everything with the seatback oriented vertically. This ensured the stiffener was aligned with the edge of the seat.
