You will eventually over-stress the wing as designed. The glass layers on the bottom are not adequate to handle hard pullouts. I have stress cracks in the glass on both sides. I fixed them after about 100 flights with another layer of glass and re-painted the whole bottom. They showed up again. I am at 208 flights and have the cracks. I just pull up smooth and gentle now. The same cracks showed up on my son's Yellow Spit as well. It is a design issue. We are building another new spit now and have changed the whole front spar joiner to carry more load. It is a 1/8" ply spar that runs all the way through the center section and out past the gear mounts in the wing. Lightening holes applied in some areas. From 6 seasons of flying Yellow Spitfires I judge this as a required modification. Leo