So, just so i am clear, you are stating that the bicep closer to the torso is the faster movement in the video example you posted? I would think it's the opposite. As Quasi states, the bicep close to the chest creates arm bar hence the arm is extended farther and the barrel is farther out. I do agree with Bobby S somewhat on this though, that the barrel itself will be faster the farther out it is as long as the forces remain and the torso turns at the same speed. I think of the huge blades on the wind powered turbines and how ridiculously fast the ends of those things are moving.The instant your biceps disconnect, your torso, and therefore the bat head begins to slow. Watch what happens when this guy extends his arms.
The difference in speed in this example for a quarter turn is .400 sec for tight, and .800 sec for extended - double the speed. A baseball swing is roughly a quarter torso turn, but of course it uses strength and leverage and forward/stride momentum, so the time in seconds is not the same but the effect is similar.
As far as the optimal element you talk about, i agree. I am just trying to decipher if i want my DD's front arm pinned to her torso or not. I didn't think i did.
Another thing to mention, unless it starts pinned, then there must be some bend in the front elbow already, unless they are already barred. If not barred, then any lengthening and straightening of the arm has to be a leak of power in the swing.
i thought that a bent arm staying bent thru helps eliminate the leak. At least thru the start of the swing until the arms are extended and the barrel is released to whip. IMO