Shaun
Bear in mind that my rules apply only to Sat city meetings excluding Adelaide. Your results for Sat seem to include all meetings.
I've tested back to August last year and the LS profit is 86 units. Aug was a losing month with Bris contributing 7 losers straight. Interestingly, working backwards in the testing Bris has had 1 winner at $11 in the last 31 races. The recent Bris results have been the best - perhaps they have improved or maybe it's seasonal.
On the testing issue I find a good method to cover all seasons is to test the first Sat in each month for the last 12 months to get an idea of viability. Maybe the first week in each month if testing a daily system.