Alc I don't have scientific data on this but here are a couple of observations after fooling with these things for a few years. Outside of set back, props and monkeying with the pencil roll how old the boat is and if it has been beached many times and wears the pad down. I had a 1987 that was worked on at the factory too many times to count. The pad was restored with Ad-Tech(?) and after running it for many hours the material would begin to erode. It did it in a very uniform manner and as it did the boat would lift more and more. As with any structure these boats move around over time and they take on a personality of their own. It is fun to drive different boats and get the feel for different set ups but they won't run the same with the exact same set up. It reminds me of my racing days with dirt cars. You could build them absolutely identical off the same jig, same springs, same wheel weights, same stagger etc and they would handle a bit different.