Thanks again folks for all the replies. I think the diversity of replies/opinions make this site great.
I have decided to go with framing as if the crown is not present, that is laying out the insets and rafter seats without using the chalk line. I will temporarily secure the middle post to the sill by nailing a board between them then I will draw bore the middle post at the plate connection. The boarding on the shed will be vertical. As an experiment I suspended the plate between two sawhorses for about 2 weeks. The result was (without using a micrometer) that the crown went from 3/16" to 1/8" with the timber sagging under its own weight. I measured the crown (actually bow) by stretching a string across the bow. I placed the bowed face vertical so that sag in the string would not be a factor.
Amateur and having fun timber framing...Norm Hart
