People have been trying for thousands of years to fully understand what's happening when an arrow is launched from a bow. Even with high speed video equipment and all the computer power we've got now, it still ain't happened.

No matter whether the grip is at the center of the bow (as it is with some designs) or the arrow pass is at the center (as it is on other designs), you still have to contend with the basic problem that the arrow pass is several inches above the grip. You push on the grip during the draw. You push on the grip during the shot (if the grip didn't have resistance against it during the shot, the entire bow would move backward as the string moves forward) So, the grip is where all the pressures are brought to bear.

You have to balance the tiller so that the pressures are equal on either side of the fulcrum or the bow will rock back and forth during the draw and during the shot.

If the bow is rocking during the shot, the nock is moving up and down while the arrow is on the string. It will make the tail of the arrow move up and down during the launch as well. Maybe you can see the potential problem with unexplainable tail high/tail low tears when shooting through paper.

Watch this video. You can barely see the bow rock during launch. You can clearly see the rearward movement of the riser, which I referred to earlier. There is definitely a LOT of pressure applied to the grip during the shot, whether you feel it or not. But pay close attention to the closeup of the launch from the arrow rest. You can see the effect of the nock oscillating up and down on the string. This bow isn't bad, but it could stand a little bit of work done to it.

http://www.youtube.com/watch?v=hDV1pHtI7S8

Wouldn't it be great to have a high speed camera as part of your bow tuning gear?

Here are some more slo-mo videos, just for the heckuvit. These are pretty old, but still interesting, especially for fingers shooters.

http://www.youtube.com/watch?v=48R2ajWx3rY