A good complete framework is valuable because the pieces are compatible backward and foreward. The value of a usable frame is the total value if the skin is no good or near it's lifespan. Replacement skins are so expensive. Over $1800 ten years ago.If I wanted one I would probably pay $400 for a good quality, complete frame because I can afford the price of a new skin.
Be aware that folders in generals are a special market and Kleppers are a special market segment of their own. Used high-end folders, especially Kleppers, adhere to the Antiques Road Show philosophy. To maintain the value it has to be unltered. Any obvious changes or funky repairs make it just another used kayak. But any money spent to bring a Klepper back to original specs increases the value of that boat by about the amount invested. So it's not like pouring money down a rat hole.

: They have a rudder option.

: Look at the Klepper America web site, shows the accessories too.

: Bill H.