gbrobbins
You could look at pt boat hulls they are hard chine and simmilar in design to fire boats , I'm sorry I dont know of any us sellers of fire boats or (firefloat mk11) hulls. only uk sellers
http://www.kingstonmouldings.com/ amd
http://www.waverleymodels.co.uk/ and I think you have tried them there is also
http://www.deansmarine.co.uk/html/launches_5.html who sell a small boat kit 610mm and I think they may have US distributers . I got a bare hull of them as a small project and I am present doing a blog at
http://modelfireboats.com/?blogid=02 it may give you an idea of the build for any size of hull.
Peter