Hi,
What is the best method of betting or determining your bankroll size? Is it the Kelly or half Kelly? Or something else?
THEORETICALLY: the kelly
AS PRESENTED IN LEADING HANDICAPPING and WAGERING BOOKS: the half kelly.
REALITY: SOMETHING ELSE!!!
The starting point to consistent profits is to identify 20/20 Factors that is 20%POT and a 20% S/R,
Using only 1 or 2 factors on their own or combined, once these 20/20 are identified the kelly criterion provides the best known method to increase your bankroll, but it also carries substantial risk for eroding your bankroll.
So you need to find a balance between Risk and Reward.

The KELLY CRITERION provides for MAXIMUM BANKROLL GROWTH over any extended Profit Determination Periods, it does not provide for MINIMUM RISK. Let me explain:
1. PURE KELLY: REQUIRES YOU TO DETERMINE YOUR POSITIVE EDGE, AND BET THIS PERCENTAGE OF YOUR BANKROLL ON EACH WAGER. The primary problem with this strategy is the uneven payoffs.
2. HYPER-KELLY: REQUIRES YOU TO DETERMINE YOUR POSITIVE EDGE ON EACH BET, DIVIDE THE POSITIVE EDGE BY YOUR ANTICIPATED ODDS, AND WAGER THIS PERCENTAGE OF YOUR BANKROLL ON EACH WAGER. This strategy requires you to make your computations before each race, based upon your estimate of each entrant's probability of winning and the tote board odds. The primary problem with this and the following strategy is the accuracy of your Probability estimates, and their reliance on Tote Board Odds.
3. HALF-KELLY: THE SAME AS HYPER-KELLY, BUT YOU WAGER NO MORE THAN 1/2 THE OPTIMUM KELLY PERCENTAGE.
4. INCREMENTAL FLAT BETTING:IT IS BASED UPON YOUR HISTORIC WIN PERCENTAGE AND AVERAGE ODDS. COMPUTE YOUR POSITIVE EDGE PRIOR TO EACH VISIT TO THE TRACK, AND DIVIDE THE POSITIVE EDGE BY YOUR AVERAGE ODDS. BET NO MORE THAN 1/2 OF THIS PERCENTAGE OF YOUR BANKROLL ON EACH WAGER FOR THE DAY. REPEAT THIS PROCESS EVERY TIME YOU GO TO THE TRACK. This is a method that is more adaptable to Greyhound Betting.
Optimum Method
To find that balance you need to know, when during your betting series the extent of your positive expectation or the negative expectation (win, loss series and the bet number), within this betting series, (look at the probabilities of flipping a coin as posted before) with this knowledge you will be able to adjust the size of the Kelly Opt. and apply this to your next bet. Always remembering that you need to have a higher avg bet size on winning bets then on losing bets.