Research a decade ago showed heavier aftermarket springs in Europe. They prescribed 4 inches of rear sag. By the no preload adjustment was left. I'd found as much preload as possible with heavier form oil. There should be a way to calculate average rider weight and spring rate for preload. I'd imagine frames breaking on Japanese bikes if Supercross with 250 pound riders. Result: 5 bulging disks with spinal cord contact..

Had a used CR-430 i will always regret losing. Should have added a rear disk and heavier flywheel. Ive wondered too if single rear shocks and linkages are better. Heavier riders dont get the springs they need past 175. ( How the heck can a 250 pound rider set preload and sag? Jockies.)