I see a couple of problems with this. For starters, in all but your 1st bet, your betting into blind pools. There are a lot of horses I'd bet at 3-1 but would pass on at 3-5.
If you are successful on your 1st 2 or 3 bets, you could be dumping a large amount at the first flash of the tote for your next race. Probably wouldn't matter too much at SA, but if it were done at Sunland, you might even make a minus pool.