The old masters did not "block in." Every single time they drew a sketch wouldn't have been blocked in it's contours would have been a more advanced less dense form than any blocking done since the 19th century and by following Bargue and these ideas you will never be able to be as good as old masters. You may be impressive on a technical level, but you will never be considered, a master.
There is no way to prove me wrong. Do not bother.