I have discussed crown in a post before with several timber framers or timber framing instructors, and each can have their own method or placement of a crown in a post.
We mostly, here at my place, put a crown in a post so that the crown is in towards the center of the building. And let the vertical siding span the gap in the crown. Because if you put the crown out and then put on vertical siding the siding would bump out.
If you use horizontal siding and the crown is in you can shim out the boards to make the true.
If you place the crown out and use horizontal siding then you have the bump out again.
So in that case you probably should plane off the crown if you're going to have the crown out.
The chalk line is just a reference line for aligning the joinery to all one plane. It doesn't mean it's the outside of the building.
Some people use the center line of the timber as a reference line.
Jim Rogers
