I think that Flounder Bay is out of business.
I've forgotten who sells the Cosine Wherry plans, but stretching the length a bit is not a big thing. Just increase the station spacing proportianally. I wouldn't go beyond 16'. I've never felt that the kits were a good deal for the money. If you have a table saw and a router table, milling the strips is not a big deal. The plus is that you can control unnevenness in coloration. If you insist, you can buy strips from www.noahsmarine.com or from www.newfound.com.. Call 'em. There can suggest other good designs.
wrote in message ups.com...
Check with Flounder Bay Lumber they have plans for an 18 foot I believe

Brian