Are the bolts in the OEM seat pan secured in such a way that they can become such an integral part of a suspension system? Did you alter them in any way...or just add springs and change the mounting bar?
No, the longer replacement bolts (through the seat pan) were not fastened to the seat pan - with a nut on outside of pan. Compressing the springs (sitting on the seat) made the new bolts (actually the rear most bolt) plunge into the seat, but not so you could feel it.
I'll add the needed nut to lock the bolt head in place but I don't think it will change the poor results I had.
Note; the oem design has the two stock bolt heads welded together.
Rider weight is predominantly aft of springs locations, so the rear-most spring took all the compression and easily bottomed out.
I see a die spring, same size, rated at 450lbs. I may try that next.
Obviously, I'm not much of a mechanical engineer. I like the leaf spring idea better but thought these springs and bolts might be an easy solution accessible to most riders.
Now that is an idea I'd never considered , instead of frame mounting the springs you could keep the floating seat and add in some springs on the lever. You could even add a second pivoting bracket to the lever to , a pan on pan design with some 2" springs in between the sections. I've seen this done with a bicycle seat before.