First off, this is an awesome action pose Really there's only one thing that I can see that might benefit from some tweaking; the left foot. The angle of the knee and the way he's stretched makes me think having his foot flat on the ground like that might mean a broken ankle Perhaps the shoe is perched at an angle on the ground, or the toes face toward the weapon. Like I said, this is an awesome action pose, and the more I'm looking at it, your proportions are spot on too! That's one of the toughest battles to fight
Feet are definitely not my specialty, and I have a habit of trying out the poses myself, but don't have a timed camera unfortunately ><.