I ran this across the last 2.5 years Saturday in Melbourne and Sydney adding only two extra rules, less than 25 lifetime starts and top 5 average prizemoney earners and came up with nearly 300 bets for about 28% win rate and a marginal profit. As you say they are worth a look if you can wean a few of the losers freehand.
However, I think Statman's Darkhorse system he sold thru PPM was similar but reports by long time users not good.