i'm trying to lay forms out on the strong back for a Night Heron. Starting from the bow i measured back the 12 inches and my final form on the strong back lands 10 3/4 " from the form on the the end form. i have "The Strip Built Sea Kayak" and in describing laying the forms on the strong back it refers to measuring 11 1/2 " from the first form on the strong back however in the book it shows a diagram of it being 12'' all the way through. I'm a bit confused this is my first kayak build would appreciate any advice!!!