I have a design which may be of interest to you. It is intended as an fast expedition double but could easily be built as a racey boat. it is a 21' x 26" double baidarka, which could be narrowed and or stretched to your fit your needs. remember that nearly the entire length of baidarkas is in the water, so a 21footer may have nearly asmuch waterline as you need.

Of course you may also enjoy building a Skin On Frame Baidarka which will probably be lighter...a project i've wanted to do myself...some day