Most of what you see of the hair is a runtime generated effect. The only real, persistent polybased 'objects' in a hair piece are the actual guide hairs. Even if the guides are made rigid enough to support the actual weight of a dynamic cloth prop, the rendered hair is generated radially from the guide hair, so some of it is going to show through the cape no matter what you do. The helmet is one standard solution; Another is making the actual hood rigid, except for the cowl folds around the face. A third option is to build a low poly invisible border within the hood, and generate the bangs or sweep that the character has without the hood, and 'cheat' (which tends to be the way the pro's do it anyway).