that whole centre section is a disgrace and shouldnt be allowed, its a major mishap just waiting to happen. as has been noted, there is very little (none) structural integrity in that section. The wing on my lady's trainer was the same, piddly little balsa brace which was replaced with ply, could have saved the effort, on the 2nd flight the wings made like a butterfly from about 5 inches past fuse each side. the main spars were barely 3/16 square, trailing and leading edges were both one piece and heavily notched for ribs with minimal if any glue. The only thing holding the wing together was the covering. Nitro Planes response after numerous calls and emails? not our problem [:'(]