My understanding is BetfairSP is pretty close to a 100% market which means its only the BF commission that creates the LOT. So backing favorites on BetfairSP people with no commission discounts would achieve a LOT of around 7%, can anyone confirm this is approximately correct?

If the above is correct you can basically create favorite or last start winner systems that might only break even or have a small LOT on TAB divvies but will actually be profitable on Betfair SP.