This may not be much information to be very helpful, but there is a fellow in Bellingham, Washington who has put some major hull extensions on the hulls of a few Nordic pilothouse cruisers. These boats have semi-planing hulls. The molds for these boats are now owned by a company in Bellingham (see photo). But Gordon Lavagier (sp?) of Bellingham Marine Repair has modified at least three Nordics with hull extensions that are at least five or six feet long. They have all incorporated a swim platform on top-- they were not enclosed extensions of the cockpit. And they were not canoe-shaped at the waterline. They were flat across the back of the boat although they were cut in at the sides to accomodate large exhaust extensions.
I don't know if the purpose of Gordon's hull extension was to improve performance, economy, or simply provide a massive platform for the storage of a fourteen or sixteen foot RIB, power launching davit, etc. It certainly makes the aft end of the boat user friendly.
You could call Gordon for more information about his hull extensions at Bellingham Marine Repair (360) 734-6326. While his company installed a new Force 10 stove/oven in our old GB36 in 1998 and he knows me by sight, I doubt he remembers my name. The Nordics I have seen that he put the extensions on were named "Y-Ark," "Well-Adjusted," and "Lavitude" (with a "v" not a "t").
The photo shows the stock hull configuration. I don't have a photo showing one of Gordon's hull extensions so you'll have to imagine this boat with a six foot platform extending aft of the transom but extending down into the water and faired into the bottom of the hull.
-- Edited by Marin at 22:11, 2008-12-27