Plastics spring back fast imo, and metal surrounded by plastic as well. The bare metal shouldn't spring back so much though, especially if you make a "sharp" bend as opposed to a "soft" one.
Kind of hard to explain but if your bending area is small you will have something like a 'V' creating a sharp bend. If you have a big bending area, it will be more round and like a 'U' and would be a soft bend. LOL