It may be due to the camera angle but, when I use your suggestion of rapidly comparing your drawing to its reference, I see the drawing as being slightly stretched vertically compared to its reference. Are you seeing that too on the video? When I was a student, this type of distortion was a common issue for those of us who didn't begin a drawing with an envelope that established the overall proportions of the image. What are your thoughts about using measured envelopes as a beginning, as Raphael Ellender teaches in his book, Basic Drawing? BTW, Andrew Loomis offers a "visual survey" on page 88 of, Figure Drawing For All It's Worth, that's kind of similar to your "inside to outside" method of measuring.