Here is a site in NZ that sells kite sails. I've been watching the kite-boarders out here in Port Gardner, Wa and it looks to be a pretty good idea. I'll try to get some pictures this afternoon. I've been considering a kit-spinnaker myself for the ease of single handing.
Today the tide was up so I could get in the shallows where these guys play. They can actually go up about 2-3 points on a beam reach and they were passing me up doing 8 kn. You can see the wake they're kicking up.
I have seen a picture of a spinnaker that had a central section that looked like an eyebrow. This was actually an airfoil that acted rather like a modern performance parachute and created lift. Apparently made an enormous difference in light airs.