Ralph Vince worked close with Larry Williams. They started by using full Kelly to optimize their profits. In the beginning they were very successful, but soon enough they hit a losing streak, a huge drawdown, and lost a lot of their money and customers. Vince eventually came out with a new formula to use a fractional Kelly, and Larry's recommended percentages are based on Vince's later research.
Quote from Daal:
Doesnt bother you the fact that you could make more if you had risked a little bit more. As ralph vince says "if you are not trading for optimal
profits, then you belong on a psychiatristâs couch rather than in the
marketsâ. Of course his optimal F is suicide but he still makes a good point
