If it were me, and maybe it will be one day, if looking for a material that is dimensionally stable and easy to work with I may not go any further than plywood.
Instead of bending the radius, I would be thinking about cutting out the radius from at least two layers of quality plywood laminated together with staggered seams. Without doing the math on arc depth for a 35' radius 12' long arc, let's say you have a 1 foot deep curve. With say a 6 inch deep plywood strip that's 18" or so and you could cut 3 or 4 such strips from a single sheet. Maybe my guesswork is off, point is material cost will be neigible.
After laminating a couple of strips together and cutting the curve, I'd sand it as close as I could to the desired profile (not that hard, I recently did this for the sides of 5 foot tall curved line array speakers). And then I'd finish the face with another strip of ply bent and glued along the curve. That would provide not only a very smooth curve, but add dimensional stability in an orthogonal direction. Depending on depth of the laminated ply strips and thickness of the bent face strip you could get some springback that tries to deform the curve. Going to 1/4" or 1/2" ply for the bent face would minimize this. Some experimenting may be needed to find necessary depth of the arc segments.
Last edited by Bigus; 07-01-2019 at 05:48 AM.