My first reaction... since David is orthodox and you are south paw, you should have stood in reverse, or maybe you were trying to keep it all secret?

Second, if you are matched leads, you pak sau and gwa choih quite well... since you are not matched, you are advocating a double trapping movement before you even throw the punch. I'd guess that most of the time, the punch would retract before this would be successful

Third, much to be said for what Sanjuro said, hit someone HARD and it drives them backward.. this doesn't seem to be accounted for?