Originally Posted by Despos
No one correct answer. Its arbitrary somewhat and dependent on the style of vest or the cutter/fitter's point of view. The height would relate more to the armhole of your shirt than the jacket.
If my shirt has high armhole, how close should the armhole on a fitted waistcoat be relative to the shirt? 1 or 2 cm allowance? Also, has any one put a "slit" on the side of a waistcoat on the lower part of the armhole?