According to the plans you glue a 1-1/4" wide strip of 1/16" plywood to the outer end of the top and bottom of each rib with a 1/4"x1/4" stiffener running slightly inboard or along the outer edge. I used a 1-1/16" wide piece because I'm using a slightly different closure design (Iron Designs). My 1/4"x1/4" strips are shown in the 1st photo. I also added balsa strips that I beveled so my fiberglass cove cover would fit properly. I made the fiberglass cover by epoxying a layer of FG cloth over a 4" PVC tube coated with carnauba wax.