Because there's a surface with bi-directional curvature, you'd have to define a deformation area. This will be based on prior knowledge of how this geometry/material behaves in the deformation process when you bend up the flat. Unbending is standard for surfaces with curvature in one direction only, like cylindrical surfaces.
Also make sure you have valid "fixed geometry" to use as unbending reference. Version 1 doesn't have that.
