Joined: May 2002
Martino Rizzotti published a book, Early Evolution, in 2000, which presents a reasonably detailed scenario deriving the flagellum from an F1F0 ATPase. Compared to other options it is not particularly convincing, although he does rather better at it than one might otherwise expect.
But, it is published, here are some online links:
Cavalier-Smith was fairly critical of the book in his review, but does cite the flagellum scenario in passing in one of his articles.