Originally posted by Phil C
U got it wrong there mate. Moving the bottom of the shock outwards (towards the wheel) makes the suspension progressively softer throughout the movement, thus giving the effect of a softer spring. Moving it inwards makes it less progressive thus giving the feeling of a stiffer spring.
Try working it out by drawing little diagrams an using triganometry.
I think you'll find Dragonfire is in fact correct. Moving the lower shock mounting point out on the arm (toward the wheel) makes it firmer due to less leverage applied to the spring - ie closer to the wheel, less leverage applied, further in on arm, more leverage applied.