I always build my wheels in the front fork or rear frame and aim for the middle of the location it has to do it's job in. Works fine for me. You also compensate the wheel for a slightly bent rear frame this way. The middle of the rear rim has to line up with the two down tubes from the front frame. This works best when not to many components are fitted to the frame which isn't always the case of course when you have to rebuild your wheel.
