I think acceleration mechanics start to take care of themselves when you add load. Think of it this way, and bobsledding provides a great example of this, but I am going to use another analogy. If you have to push a car what do you have to do? Lean and drive. When the car starts to get going what happens? You start to straighten up and push with less force to keep the car moving. The more you do it the better you get. When you switch to no load, you should see fewer technical errors and a greater impulse. Also working with loads allows slower movements and its easier to correct defeciencies.
