I dislike your method for so many reasons.
Presumably if the first favorite doesn't win and the second one is short you have to bump up your bet a bit. Then if that doesn't win you bump it up a bit more. etc., etc., etc. Like Davez says not the best investment strategy.
Secondly, what if you win your first race, what do you do for the rest of the day? No, punting is an ongoing thing for me - I enjoy it - none of this quit while your ahead crap, let's get more ahead.
Thirdly, pick the favorite in every race? I might as well buy lottery tickets. Working out which is the best horse is much more challenging than which is the shortest priced one. I Punt as an intellectual challenge, not the for buzz of putting a bet on.
Fourthly. Nah, I've had enough and you probably have too. :-)

KV