How by doing all of these measurements are you going to ensure that you are staying within the SOP type and guidelines?
The SOP states weights, tail angles, and gives suggestions as to what medium head width(pg28), broad back(pg 29) etc.
I do like the description of the head- it should be strong, moderately long, well filled in forward of the eyes to avoid crow head, with skull somewhat flat on top rather than round. And I would take the description they give in the head section that includes Cornish or other meat types "where a more massive type of head is more appropriate.
So to me you need visual as well as possible measurements. The issue is the judges aren't going to "measure" the birds body parts. It's a visual/feel for them.