Try running your current shock to the max preload and ride it awhile. How does it compare to your current setting? How much static sag does your bike have with the current settings?
If money is no object and you want superior performance Wilbers makes a great product:
Suspension for big Chopper and Cruiser. The Wilbers stereo shock absorbers with a piston diameter of 46 mm and compression reservoir optically as well as functionally adapt to the look of big Chopper and Cruiser motorcycles! Robust and reliable with excellent response behavior they are fully...
epmperformance.com