For C11000, this hardness corresponds to a cold worked H01 temper (1/4 hard), HRF range 60-84 --- ASTM B152. Maximum elongation is 35% vs. 50% for annealed.
I’m not expert at forming sheet metal, but from data for forming aluminum alloy of 35% elongation, it appears: If forming is done in a brake press with lubricated male and female dies, a 90o bend with 0o inside radius can be achieved. However, without dies, e.g., by bending over an edge, the material will stretch and thin, and cracks will appear in the outside surface.
For the latter, unconstrained case, I estimate a minimum inside radius of at least 5/8” is necessary to avoid elongation greater than 35% for the outside surface of the copper sheet.
Anyone with experience: please feel free to comment.