Actually its because of the leaves progressive rate that flutter stacks aren't used. Typically they are soft at first and ramp up quickly on larger hits. But because of their stiffer rates, higher speeds aren't handeled so well. As for little rebound, I've found the opposite. The Bilstein numbers are deceptive because they use Newtons, 255/70 sounds like it would be lite but rebound forces are up to 5x's less then compression forces. So 70 may be heavy.