ok that confused me...you said
bets: 838, returned $588, 79 winners, ROI 70%
bets: 627, returned $473, 65 winners, ROI 75.5%

is that profit or loss...looks like a loss to me....
i have never really looked in to this but have used it some times for huge winners....i think it works best if the horses were say with in 3 lengths last start