Speedmaster Any Wilbur (or Other Brand) Front Fork Springs Experience On 1200 Booneville Speedmaster?

My 2018 speedmaster is obviously short in front shocks efficiency, specially with passenger.

The only option I am able to find comes from wilbur. They offer a set of fork springs for the speedmaster. It seems there are other options for the bobber, but no for the speedmaster.

Strangely, they note in the description that there is a need to "reduce bushes". I am not sure what "bushes" they mean... there are not such bushes in the parts diagram - while I suspect they mean reducing two separators that seem to add space like some sort of preload, but look like not adjustable in any manner.

¿Some experience of somebody using those wilbur springs, in this or other model? ¿do someone know about such reduction and how it is supposed to be accomplished?

¿Some alternatives?