Show me a Kawasaki seat pan in perfect condition and I would wager that I could show you a sled that has never been ridden. As a matter of fact, I have yet to see a seat pan that didn't need some degree of repair. We have found that the seat pan plastic responds nicely to the same PVC solvent that you would use to connect PVC pipe. We cannibalize a badly damaged pan and use the parts to reinforce cracked or broken parts of other pans - usually the corners and mounting points.
We have two seats in process in the shop right now so I thought it would be a good time for a photo.
Once rehabbed for the front attachment we add a strip of plywood and new stainless steel "tee" nuts. In the rear we change the attachment point and drill new holes through the glove box hinges and then use a stainless 1/4 - 20 x 1 bolt and nylon lock nut in each hinge.