Have you asked on
http://modelfireboats.com/index.html
if not give it a try, there are a few plans knocking about but they all seem to be old aerokits plans with no frame's on them , there is a chap who sells from canada on ebay that has plans but they are expensive , ask on the site above. it is dedicated to them also try
http://groups.yahoo.com/group/firefloat/ there are some of the original builders plans on there, but not enough to build but all the detail
peter