Welcome New Punter.
Your first idea I have run back to the start of 2010 and the results are as follows. :-

Meetings considered : 2642
Win Strike Rate/Seln. : 39.0%
Plc Strike Rate/Seln. : 66.0%
Average Win Dividend : $2.06
Average Plc Dividend : $1.36

WIN
Races Bet: 157
Races Won: 62
S.R./Race: 39.5%
Outlay($): 159.00
Return : 127.60
$ Profit : -31.40
% P.O.T. : -19.7%

Not worth going back any further.

Enjay