Tom Doak -
I disagree that you should avoid speculation in a biography. With your experience as an architect, your knowledge of MacK and your natural eloquence, I can think of no one better positioned to speculate about MacK. I implore you to do so. I think that is what I missed in your very fine bio. I never thought I would say this to you of all people, but don't be so #@*#@ humble.
A biography of Jane Austen was published a couple of years ago. Austen left very little biographical information. Her brothers and sisters burned her letters. She never married and died very young. We know her birth and death dates, her novels and 5 surviving letters.
Claire Tomalin's bio was a tour de force. Won every literary prize around. Virtually the entire biogrpahy consisted of informed, reasoned speculation about Austen's life. Even if her papers are magically discovered someday and Tomalin's speculations turn out to be flat wrong, anyone who read the book learned lots about Austen's world and how it was incorporated into her novels. Get the book. Even if you have no interest in Austen (and you should) it is an object lesson in how informed, responsible speculation can deepen our understanding of a subject and make for a damn good biography.
TEP -
I had you and Wayne in mind when I referred to an archie's notes and drawings. No one left a better written record than Flynn. I'm sure there are gaps, but Flynn left much more than most. Use the hell out of them and when the historical record runs out, indulge in the same "informed, responsible speculation" I urged on Tom Doak above.
As Tom D is an expert on MacK, no one will know more about Flynn than you and Wayne. You are our best guides to his creative process. Don't keep your speculations under a bushel basket.
If you do the hard, honest work of historical research, you earn the right to speculate (to the extent consistent with the known facts, of course).
More generally, I think the archie bios to date have seen their main task to be the collection of info on their subject's lives and works. No one had done this important work before. TD, Brad, George and others have done a wonderful job organizing and preserving all that information. God bless 'em. And I love their books.
But there is a second act to these things. And part of the next act will be to develop deeper insight into the work of these archies, figure out who influenced whom, identify strong points, weak points, etc. In short, the next stage should reflect the same kind of scholarship that surrounds any art form. That's the direction I hope archie bios take in the future.
Again, just some thoughts.
Bob