Hi Bill. The native peoples apparently built larger SOFs including two and three hole kayaks. Check out the Morris book; He's got boats of all shapes and sizes. The Dyson book also has some interesting large baidarkas in it. I found both books at my local public library.

There are all types of building techniques but you generally don't need station molds because the rib geometry is not very complex and it is the stringers that actually form the shape of the hull. I built my open decked kayak for hauling kids around. It is a regular tandem kayak with an altered cockpit arrangement. I can fit two adults and two kids no problem... the limiting factor is safety (i.e. how many squirts could I rescue in a bind).

Good luck with it,
Chip
www.ChipSandresky.com