Haven't added decks to a Sassafras, but to a different 3 plank canoe. On a 14'8" canoe, I added bulheads 3.5 feet from the from and 4 feet from the back. I decked the front 4.5-5 feet and the last 4 feet, with a 3 inch "rail" inbetween. Pros--Alot of stiffness, alot drier. Cons--heavier, more challenging to build, and slightly more challenging to load.

   Thanks for the post but not really intending to extend the existing decks or bulkheads. Just adding a bit of refinement using strips instead of the solid wood provided. I ordered my kit yesterday. Once it gets here and construction proceeds I will look at options.