Taking another angle on this, I recently made two adjustments to my grip that have improved my consistency; tightened the palm shelf a little so that the grip has more of a hold on my hand than the other way around, and increased the rake of the grip to get my wrist into more of a 'locked' position.
The weight of the pistol is shared between the top of the middle finger and bottom the wrist, I am continuing to train my thumb to stay out of the action and causing flyers!