Dave: I always make a profile drawing/blueprint of my rifle and pistol builds so I can see the relationship of the parts . That way, there are no surprises of the negative kind.
To make these profile drawings, I start by drawing the barrel full scale, marking the end of the breech plug threaded journal, and thus, the vent hole. Next, the lock plate is superimposed over the barrel and drawn in. I make a black dot with a felt pen on the outside of the lock plate where the sear arm is so that I can now locate the position of the trigger(s). Once the trigger(s) have been added to the drawing, it is easy to determine the length of pull and where the butt plate goes. Positioning the butt plate also has lots to do with the drop you want at the comb and at the heel. Drawing in the outline of the buttstock follows naturally now, taking into consideration the school of the rifle and any other idiosyncrasies it may have.