GL1800 rear spring rates

I'm new to this forum but will probably be back again and again, given the build project I have underway.

I'm building a GL1100/1800 reverse trike and need some information about rear spring rates for the GL1800 suspension. I'm eliminating the computer-controlled suspension tuning and just need a suitable base spring rate that I can 'tune' mechanically. My 'shopping' has turned up several suppliers of 'improved' and 'stiffer' springs, but the suppliers provide no information on actual spring rates. Honda is no better in that there is no spring-rate info in the monster service/repair manual I purchased in the hope of learning the specifications for my fresh GL1800 rear-suspension scheme.

I have some experience with spring rates on racecar suspension and feel I can probably interpolate what my trike will require vs. the needs of the motorcycle -- if I know the baseline spring rate.

Thanks in advance for any and all help.

Mike Bishop
Santa Rosa, California