Crash,

You can easily lay all the favs. So I am not sure what your saying - unless you are saying lay them at the SP price which would be difficult.

Regardless if you lay or bet on the favs on betfair you are going to come out at a near break even price ( possibly down a % point or 2 due to commisions) as a lot of studies have shown but you won't be down 10% or 15%. It will be around 1%-2% instead. And hence the possible approach of using a staking system that reclaims this 1%-2% and puts the overall plan in profit. The possible reason it works is because over time the 1%-2% loss actually moves in and out of profit ( 1%-2% up sometimes and and 1% - 2% down sometimes ).

Good Luck