I cut the materials needed to fabricate the diagonal wing braces. Tube is .049” 4130 steel, lugs are also 4130 and the adjustable ends are made of aluminum. I’m not certain of the grade of the aluminum parts, but they were from a B-727 engine torque tube, passed along by a friend from old (new) American Airlines inventory here in Tulsa… a component that likely saw repeated stresses, so I’m not too concerned that they aren’t up to the task. The primary purpose of these tubes is to keep the wing from shifting fore and aft… the most critical being forward in a sudden stoppage, meaning that their most critical function would be performed in compression. Some build these from wood, and while they may look nice, they likely do not provide the necessary strength required in this critical area. I would like to build mine of wood to match some of my other components, but for improved durability and safety, I’m following the recommendation of others and using steel.