I've purchased a number of Corbin seats and I also discovered that they are almost a hard as a nice piece of plywood. What very few guys seem to know is that you can special order a custom seat from Corbin to your specs at no extra cost. My last purchase had real leather instead of vinyl, moved the bucket forward 1 1/2", soft 1/2" padded panels added under the top skin, and other changes, all for no extra cost. The result is a very comfortable seat, completely unlike the 'off the shelf' seat. Only the Corbin California branch will do this. I recommend the following procedure:
1. Order a Corbin catalog. It's a big color catalog illustrating just about every bike made and the corresponding seats. You can select any basic design (within reason). You cannot, for example, get a Gold Wing style seat for your ZX-250. In my case, I liked the seat shown on the Honda ST-1100 much better than what was pictured on a ZX-11, so a wanted mine constructed that way. No problem.
2. I wanted the seat step moved forward a little to give better support and to provide a little more passenger room. No problem.
3. I also wanted some special colors. They sent me a full set of color samples. No charge. I selected black leather with a very dark ‘Yamaha’ gray for the side panels. Also, no charge.
4. Most important of all is to send them an outline of 'exactly' what you want. Don't attempt this over the phone. I also recommend that you avoid matching colors (they won't). Stick with black or other 'neutral' colors. You may later want to sell the seat or transfer it to your new bike, so you don't want special colors to become a problem.
The end result is a much better looking and far more comfortable seat.
The photo is of the seat on my 96 ZX-11. I put the seat on over 120,000 miles ago. The top is a perforated leather with sewn in 1/2" padding. Downright comfy.