Prior to 1982 the Kawasaki KZ1000 Police bike had a sprung seat, but after that the seat was hinged from the side. There is no storage under the seat. My theory is that they just wanted you to be able too lift the seat and admire the volume of wires that are located there.
After a couple of false starts, I decided to weld in a bar to carry the new sear springs. I took the seat cover off and took it to a local upholstery shop for repair. I built a "T" bar to hinge the seat. After I put the seat cover back on everything worked fine.