Henro,
I envision mine folding back about that far, but mine (in my mind anyway) would be one half inch plate that would bolt to the fender, using the existing holes, and one half inch plate that would bolt to the existing ROPS holes. Between the two plates would be 1/2 x 2" straps, with two welded to the top plate and two to the bottom. They would be spaced so the bottom straps would be on the outside of the plate and the upper ones would be on the inside. A 5/8" hole would be drilled through the four staps at one end, to allow a shaft to fit through all four straps, providing the "hinge".
At the front of the hinge, I'd flush weld (drilling through the bottom plate) a 3/4 inch pin. When you "raised" the ROPS, this pin would go through a hole in the top plate, which could be pinned for security.
Hard to describe, and I don't have a pic. Hope this conveys what I'm thinking. I'd probably run this plan by a mechanical Eng before I did it, just to make sure this hinge is NOT the weak link in the design or if I need to size up anything.
I personally think it would be as strong as the original, and I'd risk my head to it.
Ron