To be honest with you i wouldnt use that strategy because the downside is that could lose it all.
Lets take horses.. if you just a back a horse to win every race and their are 10 runners in the race, then their is a 9 our of 10 chance you will lose every race (90%) which is horrible odds..
Luckily with Matched Betting, the odds are stacked that most of our cash moves to the exchange anyway.
We make our money from risk-free, non gambling techniques and profit off bookmaker bonuse bets/bonus cash if we hit certain trigger events like ie. come 2nd or 3rd in selected races or double your winnings. Our only loss is a qualifying loss which is offset by profits which we sustain in the long term by doing all offers consistently!
Thats just my thoughts and ideas.