The point where it curls over is often referred to as "return".
There should be roughly a 1/8" return edge left on the armor pieces. The Gallery has a few excellent pics that really show this on parts of the chest and collar armor.
Some parts you may need to adjust this for comfort, as the backplate and kidney isn't really seen at those edges so I'd adjust them according to how they feel.
leaving this edge where visible gives the armor that look of depth.