Another way to estimate how your system would perform would be to estimate the results after a certain # of races, say 200 for the sake of convenience.

# of selections = 200 races x 5 horses per race = 1,000 selections
# of winners = a winner found in 79% of 200 races = 158 winners
average price per winner = $5.47

So based on $1 bets, your 1,000 selections will return $5.47 x 158 = $864.26, which means after 200 races, you could expect a loss of roughly $1,000 - $864.26 = $135.74, or alternatively, a loss on turnover (LOT) of 13.574%.

Personally I would steer clear of trying to bet on so many selections in each race. Also, one of the most important lessons I've learnt so far is that you don't have to bet in every single race. When developing a system, you should constantly be trying to think of new filters that both increases your profit on turnover (POT), as well as your strike rate. Look for similarities in the majority of your winners, as well as the majority of your losers. Weeding out more losers from your system is just as important as finding the winners.

And then when you've refined your selection process to be as good as it can be, then focus on what kind of staking plan is most appropriate. Personally I prefer betting a certain percentage of the bank on each selection, which helps preserve the bank when a run of outs strikes, but also helps compounds profits when the winners come rolling in. Hope that helps. Good luck mate.

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...time held me green and dying, though I sang in my chains like the sea. - Dylan Thomas