To get inside the ball the hips must lead. THe best way for the hips to lead is to have the upper body delayed and create upper body resistance to rotate against. A circular hand path is essential. Taking the knob inside the ball from launch is swing poison.
Ideally, the knob should go initially to the oppo batters box and the turning hips and shoulders redirect it.( this is not casting that I am talking about because the hands are rolling off the rear shoulder) A straight line hand path and a circular hip turn will not link
Drill that works ...
Point the bat tip to the direction you will hit it and in front of your helmet. ( in this case RC field). This pronates( turns it palm down at 45%) the top hand and raises the rear elbow. Stride to balance and hit. Let your upper body do what it will do naturally. The only way to screw it up is to stay on the back side and spin. You will be inside the ball the right way.. The hands at launch will be almost touching the rear shoulder and the knob will point for a brief moment ( via slo-mo ) to the oppo box
Saw Mike Candrea doing this on tape at the ABCA show in Nashville. When you launch from the 45 slot from a static position( dead start) your hands stay too far from the shoulder tip and do not get in a circular path....they get pulled in a straight line toward the pitcher.
Unless you overlap the load/unload the hands
( get the hands going back as the hips rotate open) will never get close enough to the shoulder tip nor do they have a chance to launch in a circular path.
When you pronate the top hand in front of the body, the bat path is getting flat( and on plane) and sets up resistance to the lower body as the lower half rotates into toe touch. The bat come out knob to oppo box and redirects from hip/shoulder turn and flail forces the barrel to get perp to the pitch.
The measurable difference in these to techniques is the difference in the distance of the hands from rear shoulder tip at launch and the momentum and direction of the bat barrel.