Steady hold factors for kneeling position:
Support hand open, cradling the rifle
Sling smooth across the back of the hand, high in the bicep, snug, not tight
Support elbow directly underneath the rifle
Support side knee bent at a greater than 90 degree angle...extending forward
Sitting on trigger side foot
Trigger side elbow chicken winged
Firm handshake grip pulling the buttstock smartly into the shoulder
Exaggerated C-shaped trigger finger
Turkey neck, cheek weld.

The Ambidextral Gunfighter
http://www.ambgun.com