Ferd, although I did not attend the conference where the presentation was offered nor have I been instructed by Robert Chambers, I have used some of the ideas underpining this method. The regulating concepts are a level and lined log, tools that detect plumb, level and square and finally control of slicing planes at closely controlled angles. The innovation here is in the use of a template with the elliptical cutout that models the miter plane. So by straddling the log held precisely at the miter angle, the log can be marked by projecting the plane to the log thus marking the cut line. The real challenge here is to make the initial cuts into the receiving piece while retaining the material for the saddle. Then the saddle is developed and cutting is continued.
so in a way this is not to my way of thinking a scribe process but rather more of a mapping out process.