If you ever have observed a competent wrestler or judoka, you'll notice that they do their strongest arm and hand techniques close to the chest. Consider this when doing any type of tactical manipulations, including wrestling with a suspect, or even getting over a backyard fence.
Your coordination and strength is best when your hands are at shoulder level while in a bladed stance, not at your waist or navel. Your speed to defend a distraction strike to the face is almost doubled when your hands are that much closer to your face.
Knowing your body mechanics will help you in many different situations. The best example of this is the magazine change in the duty gun. Feel free to press the magazine release while the shooting hand is extended and you are pulling the gun into the chest, support hand extracting the loaded magazine. However, do the insertion close to the body. This will also encourage the other component of good tactical training: Eyes on greatest threat.
Keeping your hands close to your chest is a very good practice. In fact, when you need to send the power of your body mechanics out (picture punching, blocking, and pushing a suspect away to create distance), what hand level gives you the most power and speed?
Practice chest-level hands. Your defensive tactics stance should be remarkably similar to your shooting stance.
Above all, KISS.