I forget the guys name, but apparently he hit with V/S for about 7 years. He was in a radio interview in Canada today (TEAM radio, a national network).
Apparently when he started training with them, Venus was 12 and Serena not yet 11. Anyhow, he told quite a few fairly vague stories. Doesn't sound at all like a disgruntled ex-employee, was very complimentary towards his former employers, and mentioned a few times his admiration for Richard's game plan regarding their career. Anyhow, if you go to theteamradio.com , you might find out more about this guy and his book.