Here's a few rapid fire suggestions:
1. Keep the weight of the shoulder carriage slightly ahead of the hips. There's no need for James Bond poses just keep the shoulders slightly forward of the hips. Many, many, many (too many) shooters lean back when firing. None of them know it, they all think they're either standing upright or actually leaning forward. The reason this error persists with shooters is due to it often being hidden during slow-fire. You will see many shooters with a backward posture shoot well at the local range until they loose balance and send shots high and low. There's two penalties for not keeping the shoulders slightly forward of the hips: slower firing through the exaggeration of recoil, and extreme high and low shots which are a result of imbalance. If you find extreme high and low shots or your target, check your posture (of course, if you really fanatically focus on the front sight tip you already know this).
2. Pause your breathing. If you fire a quick string of shots while breathing they will tend to string vertically. This phenomenon is called zippering and its a result of the shoulders and arms being "notched up" with every rise of the chest. Don't grab a lung full of air, just pause the cycle.
3. Find and use your natural point-of-aim. The body is full of opposing muscles. One muscle pulls and another pushes. The body is therefore full of springs which are either stretched or contracted during activity. Muscle moves with blood and nerve but mostly through the competing actions of other muscles. So, we don't want a twisted posture during firing because the body will seek to return to a neutral relaxed position when you are no longer consciously forcing it into a stretched position. If you twist your torso to the right during rapid fire, your group will tend to cone to the left because of the body returning to a neutral orientation. A natural point of aim is a neutral standing position that does not impose a directional tension on the body. Next time you're dry-firing, sight on your target and close your eyes for three seconds. If you find that your sights moved to the left or right, you will know that your body alignment is improper. Correct by moving your feet and reorienting the body. Do not twist your torso.
The above three suggestions are better explained in the glorious and fascinating The Perfect Pistol Shot and on my marksmanship blog www.perfectpistolshot.com and, as always, I'm honored to answer any reader questions.
Practics Holistic Handgun is coming along. The edit is almost done at great strain to my editor. Cover art looks good and I still hope to have the book out this Spring. You can sign up for advanced email notification on this site's Notify Me page. Practics is a firearm defense training system informed by a lot of failures and a few successes. I hope it will add something to the overall safety of the good guys.