I ran this idea through on 3 different days:

Day 1 - 3 bets for $4.5 win all up. 66% strike rate.
Day 2 - 10 bets for $14.8 win all up. 60% strike rate.
Day 3 - 14 bets for $19.2 win all up. 50% strike rate.

I did give all favourites less than $2 a miss. I usually steer away from favourite backing (I like the longshots!) - but this idea seems to have something behind it!