Sad Flower in the Sand
The only problem I had with it is that the first two or three chapters (how ever far I got...) is that it rehashed the other two biographies that I read. I should probably have skipped ahead and tried to find something I hadn't read about yet, but... eh...Bill McKeen, author of Outlaw Journalist: The Life And Times of Hunter S. Thompson (along with many HST articles, interviews, and I think another bio some time ago) is not aware of any contact between them.
He is looking into it for me, and I will post anything he finds/passes on. Virtually everything HST discussed in this thread and a shitload more is in aforementioned tome. Outlaw is worth the price of admission.