hey Neil, sorry I missed your post somehow (btw, I marked your topic about the swap, I love watching it, it's like a discussion between 2 rhetoricians =p)
Go here to see what happens if you don't complement them properly
if you went to my link redirect above, you will see how the springs work alongside with the shocks.. When you say valving too high, it actually is generally said too light or too heavy. High (or lack of) usually talks about the resistance-to-moving correlation of the energy (kinetic) through the shock.
You are right about the downside; if it is too light, the ''shock'' received that is transmitted as kinetic energy through this suspension components system will in turn allow the wheel to continue moving upward, thus the tires become unloaded at a given instance as the unsprung weight is moving upward from a ''road shock.'' Too heavy, and the resistance-to-moving correlation is too high and the kinetic energy is then transferred to the body, or chassis. Please keep in mind, this is when you hit an irregularity in the road surface for the compression damping of a shock.
For the rebound damping it's a little different. Often we don't talk about it being too light, but if it's way too heavy, the resistance-to-moving correlation of the shock is, again, high, making the wheel not return to its previous state [effectively.] If you are successful in overloading a tire, the car's weight will bottom out the suspension.
Since you have given a spring rate, you can actually have shocks tailored to them. To do so (you can check out our sponsor that does Koni rebuilds) people use what is called a damper dynanometer (often referred to as a shock absorber dynanometer as well.)
''...performance is measured as the resistive force that the shock exerts when the dyno tries to compress it. Since shock stiffness is proportional to the rate at which the shock is compressed, then the shock dyno measures the shock resistance for different speeds.''
''...the performance of a shock is different depending on whether the shock is being compressed or extended. Thus the shock dyno measures the resistive force offered by a shock when it is both compressed and extended at various rates (velocities).''
''The data from a shock dyno is plotted as a pair of curves. one curve for compression and one for rebound. The curves represent resistive force VS shock velocity.''
''However, to differentiate the curves for compression and rebound, one is plotted with resistive force in the positive y-direction and the other is plotted with resistive force in the negative y-direction.''
~P2P