On #3 It is because the shape of the hull on the inside is different to that on the outside, so the water flow at the back of the boat is not quite straight. Next time your at the boat have a look at the direction the water will come off the inside and the outside and you will see why the trailing edges need to be further apart than the leading edges.
If you are not sure on this send me an email on [email protected] and i'll send you a picture explaining it all.