Just a thought
would the front fork springs from a heavier bike fit in the front fork tubes?
I've been searching for info on this myself. Springs aren't that expensive, but I've already bought a bunch of parts... have to stop at some point.
I went to this site that list forks by diameter
http://organ-donor.org/motorcycle-data/fork-tube-diameter-list/#tube37
I compared bikes listed to the GS500
Then looked at the Progressive specs for size and rate of their recommended replacement springs for the bikes.
Specs here https://www.progressivesuspension.com/assets/files/7100-105-Specs-And-Tech-Info.pdf
Progressive list the 11-1128 .54/.80 (35/50) for the GS500.
A lot of the bikes from the organ donor 37mm list take the same 11-1128 spring as the GS500, so I figure those other bikes stock springs are just as weak.
I was looking for something that uses a stronger replacement spring. The Honda CBR600 (1988 or so)
Is a candidate as it take the progressive 11-1129 spring a .63/.89 spring.
Another option might be used stock 39mm Sportster springs (1984-2003). The standard progressive replacement is a .63/.89 spring
The used stock Sportster springs are mushy for a 500 lb bike, but might be an option for the 375 lb GS500. I looked at those because I think I have a used set out of a Sportster. The length and diameter look ok if going by the Progressive spring chart.
Of course my logic may be highly flawed here, but if I can find those Sportster springs, I'll try them.
Good luck looking and let me know. :woohoo: