Without getting into the RVP (RightView Pro) description of "addition" ... let me simply state that there is a common position, that has been identified by several hitting systems, in which the high-level swing passes through.
o The RVP system refers to it as the "Connection Point".
o Mankin refers to it as the "Power-V" position.
o Emanski refers to it as the "Explosion Point" position.
o HI refers to it as the "Swearing In Position".
o Yeager refers to it as "Down through the nipple".
They all refer to this position shown below ...
In the above clips you can see the "Power-V" position highlighted in 'red' ... that being a pinched forearm-to-bicep as the hands pass by the rear shoulder ... aligning the hands, rear shoulder, rear elbow, and rear hip.
Then there is the "Lazy-L" position, which you'll want to avoid ....
And then there is the flaw in which the rear elbow is seen to be ahead, at this position, which many people use as confirmation of 'bat drag'. That said, a good swing will boarder on 'bat drag' ... and hence I'm not a big fan of ultra conservative approaches that restrict 'bat drag' to the point of taking a kid 'away from the pattern'.
Epstein calls it the Universal Launch Position. He also refers to the position that Bonds gets in at the end of his clip, the Torque Position. This is the position I look for when working with players. If a hitter can get into this Torque position on time, they are in really good position to hit the ball.