When Costume making a hair system, there are many details to keep in mind. One very important is the direction in which you want to hair to go. One simple way of explaining this in hair terms is to look at partings; a centre parting can remove width from a forehead, whilst a side parting can help to make the face appear wider. Look at your hair as design and consider the overall shape, weight, width and line.
Remember the direction we tie the hairs in, will be the way the hairs wants to lie on your hair system. This could be used in reverse to create permanent lift on your unit, but on the whole you want to tie the hairs in the direction the hair would grow on the head. Usually toward the back of the head.