It has been found over the years that the OTW does have a weak spot in the fuselage. Granted, to discover this weak point takes a very very hard landing before it will show up. This weak spot is between the bulk head immediately behind the rear seat and extends to the next rib which is immediately behind the luggage compartment. The best way to stiffen this area is to install four stiffeners, two on each side of the fuselage. Use 2024-T3 aluminum 1 inch angle cut to fit between the ribs as extra longerons. Position one 5″ above the lap joined formed by the top skin of the fuselage overlapping the side skin, and one even with the baggage compartment floor. This should place the bottom stiffener about 7.5 inches below the lap joint. Use 5/16″ rivets with 1″ spacing. Do not use countersunk rivets.