Dont confuse the diameter of the forks with the diameter of the fork springs. It is my understanding that a 4860 fork has a 48mm tube so this number does not speak to the spring diameter.
On my '02 Adenture I shortened the fork 2 inches to lower the bike. that entailed a travel limiter piece internally and cutting the spring 2 inches shorter. Stock the rate was .44 but cut two inces shorter it became a .49. This rate change was measured by Canonracecraft. They can cut your springs or wind you new ones. You can do it yourself too. I did.
hack em, heat em flatten the coil and grind the coil flat. An Oxy-act heating tip cuts and bends them fast.
The preload caps on the adjustable models allow a 10mm variability plus you can preload the springs internally with spacers on the non adjustable caps.
I know you guys are concerned about spring rates but you are wrong in my opinion to place all the responsibility for how the fork works or doesn't on the rate. Actually the damping and the airspring are much more important in how things feel/work up front...and in the rear.
Honestly I don't think you will solve the problems without a revalve and subtanks up front and a revalve in the rear.
Z dog has published the correct shims to use for a revalve upfront and will do our rear shock for resonable money and he can help you with spring selection. He knows the vendors.
Drop the cash and be done with it.
Throw in a scott's steering stabilizer....
The results will blow your mind.
I hit a gut pile on I-5 the other night. The bike never even moved out of line.
Bup-bup and I was over it at 65 mph.
It's a saftey issue and your ass is on the line.