Do you have pictures available? The link you shared really doesn’t show much. I’d be interested to see interior, exterior, engine compartment and under carriage.
I pulled the 6" Dobinson springs and went down to 4" Slee springs. I now have zero vibrations and the ride is so much smoother. I'm not dogging on Dobinson, the springs were there super heavy duty springs, and I don't have enough weight to make them ride like they should.