I would like to include a 3/16 to 1/4 inch cast off on my early Lancaster rifle scratch build. How does that work? Is the centerline of the butt plate off set and parallel to the centerline of the barrel? If not then at what point do the two intersect? I read "Recreating the America Long Rifle" but it was vague about how to lay that out. Bill Raby demonstrates this as laid out parallel.