Keeping the crossbar barely out of the water would be interesting..
The transom is the flat part at the back of the hull, where the rudders go. If the stern is too low, the water will swirl around from the sides and create turbulence behind the transom. That is wasted energy where you are pushing more water around than you need to, so by moving weight forward a bit you lift the transoms clear of the flow. Then the water breaks away from the hull smoothly without that turbulence.
Once you know what you are trying to achieve, you can hear it. You will always have some noise from the rudders cutting through the water, but the turbulence I speak of can be created and destroyed pretty easily with weight shifts. In light to medium air it's really easy to see what I'm talking about.