Another way to increase the stiffness, or to increase the travel of the shock....
Would be to change the angle of force applied to the shock.
ie
Using the same shock absorber, but applying the force "thru" a lever would either increase or decrease the travel... thus increase or decrease the amount of travel / force needed to compress the spring.
eg
Change from say the way the suspension of the 8297 works....wheel travel up thru the shock absorber..
To say the way the 8465 or 8458 "silver champion....where the wheel travel travels thru a lever then up thru the shock absorber.